OUR ENVIRONMENT in 30 Minutes || Mind Map Series for Class 10th

[@PW-Foundation]

Check Batch Here: physicswallah.onelink.me/ZAZB/YT2June 📲 PW App/Website: physicswallah.onelink.me/ZAZB/PWAppWEb 📚 PW Store: physicswallah.onelink.me/ZAZB/vsff3zl9 🌐 Telegram: t.me/foundationwallah

[@Rock_Blue]

Yeh yeh yeh

[@alpana_craft]

Control and coordination please

[@jobancrew0744]

@@raghavhariom2712 uska weightage nahi hai...

[@gaming_ff90299]

[@aaaa4uuu]

Kabse interact interact bol rhi ho hindi bhi bolo sudhh

[@omprakashprajapati536]

Board walo like thoko🥲😂2023-24

[@shreyamishra872]

Kal h mera pre board

[@ManojSharma-pf1fu]

Kal ha Mera pre bord ha 😢

[@pvp_king_001]

Mera pre board h

[@killerrocky9975]

Pdh lo comment krne se kuch nhi aayega 😂​@@shreyamishra872

[@shashiney]

Abhi 9ghante m ppr h. Pata ni kya hoga

[@asfishaikh427]

I hope everyone achieve 95% + scores in Science subject 🙂

[@thakur7565]

Sike...

[@khushu32-1]

Thanku bro is wish ki kaafi jyaade jaroorat thi kl science k exam hi

[@spjaat7105]

Thnx bro

[@Aarizshaikh108]

@@khushu32-1 hiii

[@JayYadav-cp7tr]

Tankas😭🥹❤️

[@kidsyogawithshivi2691]

1:22 Meaning of Environment 2:15 Ecosystem 3:53 Types of Ecosystem 6:10 Components of Ecosystem 11:51 Food Chain 15:39 Food Web 16:39 Trophic Level 18:05 10% Law of Energy 22:46 Biomagnification 24:52 Ozone Layer (Depletion), Solid water and their disposal You can thank me by giving a like..👍🏻

[@Jashan-n3x]

Thanks brother

[@AbdulWaheed-kn8zv]

Batch 2023 - 2024 all the best for board exam hope you all get 95++ in the exam, 👍👍👍👍

[@Ashiqerasool684]

This teacher is undoubtedly one of the best biology teacher in India .

[@sachinmahamuni8452]

frfrfr

[@deveshsharma1557]

She is beautifull also

[@Ashiqerasool684]

@@deveshsharma1557 A person should be seen by his her inner beauty not how one looks from outside

[@Ashiqerasool684]

@@sachinmahamuni8452 haven't got

[@shivathakur7744]

@@Ashiqerasool684 bro diary of Anne frank ki theme padh ki kya 😂

[@amrit_singh_10]

All the best for science exam... I hope all of you get 95% marks...

[@arpitgaming2360]

95 percent nhi 100 percent chahiya

[@lpsgamingyt6472]

@@arpitgaming2360 bhool jaao 99 aa skte h 100 kbhi nhi

[@nohope1877]

😀😀 aa gaya 95% wala comment 😂

[@bhoomikasaini5070]

Esi hi bolre ho tum hmara dil rkhne k liye 😂🥺🥂

[@vinodkumar-hz5qi]

Dar lagrha hai🥹

[@sweetyverma7402]

All the best 👍🏻 tomorrow science paper 🗞️🗞️🗞️🗞️

[@iittopper990]

No after 2 hours my exam is

[@Progamer-rx6dn]

@@iittopper990 kesa gaya

[@aqua_pocky]

​@@Progamer-rx6dnme too lol I have my paper after 5 hours 😂

[@Progamer-rx6dn]

@@aqua_pocky mera bhi aaj he hai😂

[@aqua_pocky]

@@Progamer-rx6dn lol😆..... Best of luck for today 😊

[@parasparas3554]

All the best for tommorows Preboard😊

[@monalisasamal9592]

How do you know that my science preboard is tomorrow? 😂😂😂

[@asthajat6548]

Parso hi board exam hai mein aaj phali bar yeh chapter padh rahi hu 💀

[@abdulqayoom7497]

😂😂😂😂

[@harsimranjeetkaur2970]

Waah

[@Woahits_me]

This 30 min revision is life saving!!! 😭🤍

[@KimTaejzy1120]

ofcourse 😂

[@Euphoria.7091]

Damn True

[@Shubham.chaturvedi04]

No doubt that she is the best biology teacher in India. Thank you so much for making biology easy for us. 😇😇

[@G.Gamerz699]

Go nd study with shipra mam(adda 247) I m not in support with her channel but she is unbeatable..

[@cyberxcrimnal1342]

Bhai bio easy hee hota hai 🤣🤣

[@shashwatraj7066]

@@cyberxcrimnal1342 kuch bhi mat bol bhai tere liye easy hogi kmse km mere liye toh nai h

[@WhytheNandz]

Biology aid

[@shauryafact10]

Absolutely right broo

[@John_Wick720]

I wish everyone get 100 percentage in thier board exam 😁😂 Thanks for so many likes 🥰

[@Pandeyji___646]

Thank you

[@editwfallen]

You wish 😸

[@Thegame_07]

Theek hai sab topper

[@pranav1650]

First of all tommer is my preboards first i want pass it ,🥲🥲 idont need 100% in preboards 🤣

[@princekhan1257]

Ya

[@PriyankaSingh-ec2bt]

Kon-kon Meri tarah board exam ke 1 din pahle dekhta hai?

[@Ayeshakhan017-c3s]

🙂me to

[@Jahidul7099]

Mai bhai😅

[@rishabsingh2132]

All the best for your tomorrow 10th 2022-23 exam 🔥 🙌 👍

[@silent_voice0025]

Thank you mam ....... you explain very beautifully all topics .... Hardwork +patience +dedication = success 🔥🔥🔥🔥 Everyone who do hardwork for boards... will get 95%...

[@ALONE-BOY.01]

Tq waise di 💜

[@silent_voice0025]

@@ALONE-BOY.01 😊😊 your welcome.....

[@Shivamvilogs7895]

Hii 🙂

[@DilrajVirk-i7r]

Teri

[@theperson5020]

Watching this 2 hours before the exam 😂😂 Thank you so much @physicswallah for planning this for us!

[@Krishna_sharan]

Konse exam chal rahe hai pt test ya pre board?

[@hidiousark]

Same

[@theperson5020]

@@Krishna_sharan pre board

[@Mr.thinker-07-u8z]

I am also watching this before 1 hour in preboard exaam

[@chotagurujigamerz102]

The boys 😂👍🗿

[@priyanksehgal]

Kal kis kiska paper hai?😂😂

[@himanshubhai4305]

me

[@ashokkumarkulkarni5519]

@@himanshubhai4305 pre board hai kya

[@himanshubhai4305]

@@ashokkumarkulkarni5519 ha ho gaya science mein 60 aaye

[@priyanksehgal]

@@himanshubhai4305 bdia bhai

[@priyanksehgal]

@@himanshubhai4305 ab kl board hai

[@PriyankaSingh-ec2bt]

All the best legend for 2 March..

[@_Lokesh_Sharma_]

👍👍

[@Vidhiyadav-b9j]

😢😢

[@rehanbatt01]

I pray for all the students of 2023_24 that they get 95%+ marks in their board exams ❤🎉

[@unk667]

🎉❤

[@rehanbatt01]

@@unk667 ❤️

[@harshitchoudhary3811]

15:30 omnivorous animals can also be primary consumers

[@clashwithme6673]

@Harshwardhan Kumar when omnivorous is eating grass , he will be considered as primary consumer

[@Tanishkagaur13]

​@@clashwithme6673 DO OMNIVOROUS EAT GRASS??

[@clashwithme6673]

@@Tanishkagaur13 yup

[@savesoil2933]

@@clashwithme6673 exactly what i was thinking when watching video, so a secondary consumer is meant to be a carnivore becuse when it is consuming plants it is not secondary consumer anymore and so cant be considered omnivore

[@gayatriyadav009]

😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊

[@bhavishyavardhan8448]

Quick revision within a short period of time 😀😀 Nice explanation by mam

[@youtubers362]

🎉

[@HarshKumarXA]

Primary consumers aren't always herbivores. Human beings also eat plants but all humans are not herbivores

[@archanakale204]

Ya that's the point

[@barshadebbarma6861]

😂

[@krishkumarsinha3864]

But they are both so they are primary and secondary

[@KISAKI120]

Bro WE DO EAT ANIMALS ALSO WE ARE OMNIVORES WE ARE NOT HERBIVORES BRO THE ANIMAL WHO EAT ONLY PLANTS ARE HERBIVORES WHILE HUMANS ARE OMNIVORES AND YEAH IN SECOND TROPIC LEVEL THERE IS ALWAYS A HERBIVORE AFTER THE PRODUCER OR U CAN SAY PRIMARY CONSUMER

[@headlance7867]

@HarshKumarXA jyada scientist ban bano jo teacher ne bola hai usko follow karo

[@Neeraj.universe]

May god bless all students 90% marks aaye sabke 🤌

[@Bhangu___vlogz]

Kal board ka paper kiska ha

[@vinitameena2803]

All best everyone for tomorrow Exam 👍👍

[@jyotimanhas1338]

Thankyou 😅

[@chanchalkhandelwal9206]

Thank you

[@Grany_patidar_18]

Mam please upload concept mapping and revision video of chapter :- control and coordination......🙏

[@aayushsomani2236]

uploadedd mannnn...! go and just check once...!

[@torlly.skeleton]

Night owl jo aaj board denge we like thoke 🤪🤪🤪

[@shafanshamshad9632]

H bhai

[@niteshrajpoot1449]

Main dunga bhai aaj

[@torlly.skeleton]

@@sarthaktiwari8772 is chapter se kuch bhi important nhi hai 💀

[@MINDGAMER-f]

Bhai kitne marks aye

[@torlly.skeleton]

@@MINDGAMER-f 86%

[@Studyingisthekeytosuccess7]

Bhagwan kare sab ka set easy aaye aur pure saal ki mehnat use ho Jaye

[@Riyuuuuuuu............2882]

😢😢😢😢😢

[@Betu-s5h]

Mere aaj exams hai sab padh liya but no confidence 😢. But pw helped a lot at no cost

[@Raaj__raj]

Tommrow is my paper and I am watching videos now I started to see videos now 😅🗿

[@Raaj__raj]

Backbenchers style bro 🗿

[@kunjbeharisharma9911]

Bhai dar lag raha hai bohot

[@Raaj__raj]

​@@kunjbeharisharma9911nothing will happen all is well ❤

[@kunjbeharisharma9911]

@@Raaj__raj thanks bro for motivation Today my paper went really satisfactory

[@anuragsahani264]

Hope everyone get 74+ in science exam 😇

[@smartyboysofficial]

All best for 4 March 2023 science exam ❤️

[@tanmaypatidar6106]

Thank you..... And same to you

[@anshumangarg7466]

February Nahi March

[@tanmaypatidar6106]

@@anshumangarg7466 yes

[@AdarshKesarwani-lv4vk]

Comment pe mat dhyaan do padh lo And best of luck for Tomorrow's exam 😅

[@Priyal_sh]

😍😍😍SHE IS SUCH A BEAUTIFUL AND AMAZING TEACHER....LOVE TO HEAR HER TOOO....HER TEACHING LEVEL IS 🔥 LOVE U MY DEAR MAM YOU R FABULOUS

[@cyborggameryt4429]

Mam ki jagah board pe dhyan de

[@Priyal_sh]

@@cyborggameryt4429 oyy ullu mein ladki hu ok or mam ki bas tareef ki h

[@trackitgaming2259]

To bi bord par deyan de

[@sUnDeR..l]

😂😂😂😂

[@Beatbassbusta]

Phir bhi boards pa dhyan de​@@Priyal_sh

[@kapiltomar1042]

Ma'am plz bring the lecture on Control and Coordination.....🙏🏻

[@Cartoonworldz693]

Best of your efforts guys!!🤟 Write well⚡

[@Chhavi943]

Pre - Board -2 wala like karo 😅

[@shivanshtiwari3663]

All the best for science I hope you’re exam is going well ❤

[@divyanshishukla5229]

Same to you 😊

[@divyanshishukla5229]

All the best for tomorrow's exam 😊❤️

[@bravemasterop6159]

S2U☺️💞

[@bravemasterop6159]

Instagram use krti ho kya

[@divyanshishukla5229]

@@bravemasterop6159 nope, sorry ☺️

[@bravemasterop6159]

Acha

[@bravemasterop6159]

Fir me baat kha par krunga

[@accha_bacha07]

Let's grind in biology also friends... 👀🙂

[@bandanakumari1851]

Food chain is a sequence of an organism through which energy transferred in the form of food by the process of one organism consuming the other is known as food chain.

[@pranav1650]

Tomorrow is my preboards it really helpful for me

[@akshramodi8925]

Same 😂😘

[@heightgameryp2704]

Me to

[@lifelearning92]

To me also 😃

[@AnmolGautammgcs]

Mam your are , so beautiful ,so elegant , just looking like a wow

[@sloppyhood4079]

Legends now came to know that this chapter is also coming 😂

[@ayushmanshukla5354]

Hlo buddy

[@anmolbhai7620]

You are right man

[@Priya-bm3ir]

Schme ab pta chala hai ki ye bhi hai

[@mitali989]

Hii guys there is one more topic in this chapter I don't know there is on book or not but ya if you want to know about that so you can if u don't want to learn about it then it's your choice in my school my bio teacher teach us about : Acid rain : Along with rain the acid H2So4, and HNo3 comes to the earth it is called acid rain. Effect : 1)lose of vegetation 2) Destruction of monuments 3)skin problems And ya if you want then u can learn about it...... Thanks guys bye....

[@KISAKI120]

Ty

[@lakhansingh3958]

Thanks man

[@Arjyanshu]

Thanks broo

[@STA_AY]

Thanks man 🤍

[@hunterpro2711]

Thanks bro

[@khushu32-1]

Thanku so much mam for this revision session💗💫

[@Aradhika_097]

Hi

[@aadinandal6211]

Hi

[@rg11tube85]

Hi...

[@bhavikkamboj]

Kal kis kis ka paper h

[@anasimteyaz8318]

2024 batch waale bhi hain kya idhar?? 😂😂

[@---khan784]

Ji han hai 😅

[@sahilthakur5345]

Ji Han mai hu kl paper hai aur abhi tk mje mar rhi thi😂

[@TANU_YT_009]

Wa 😂​@@sahilthakur5345

[@TANU_YT_009]

Kl toh mera bhi hain 😢😂

[@endearing_armylink8507]

This is my first time watching ur explanation and I absolutely loved it ❤️

[@ratanrajput655]

Hello bro

[@Reels_69_random]

Going to give pre boards by just watching this lecture

[@gourithakur7136]

Mam bhot acha padhate hai aap 🥲 pura concept clear hogya

[@shivaniyadav3461]

Thanks maam 😊😊😊

[@mausamkumar3492]

kal exam kis kis ka hai 2024 me ,, attendance banaye

[@Chd_daksh_2007]

Kon kon aaya hai video dekhne exam se 1 din phle 😆😂

[@Robin1.0]

Mai

[@Chd_daksh_2007]

Good bhai dekho dekho

[@Chd_daksh_2007]

Konse school mai hai bhai tera board ?

[@parullather1056]

Tum konse state se ho

[@Chd_daksh_2007]

Mai chandigarh se

[@taestheworld2499]

Mam amazing lacture and all concept are crystal clear thank you mam ☺️☺️

[@rajvardhanpal2627]

Best series available on yt for revision 🤩😊

[@janhvitiwari1868]

Ma'am please upload Concept mapping and revision video of Chapter -: HEREDITY 😊💯🙏🏻

[@nakulgupta6462]

Hai also

[@dr.anilsharma69]

Thank you ma'am for preparing our biology for our board's exam. We loved your all videos. You are the best teacher of biology that i have ever met in my whole life. Thank you so much ma'am for your hard work for us

[@shipragupta2572]

These one shot video help so much before the exams !!

[@divyanshsharma5491]

Ma'am plz 🙏 control and coordination ka vdo bna dijeye

[@thakur7565]

I wish everyone get 95+ in board sike .... I wish everyone to get strong to bear the chappal and jhadu of papa and mummy after the results 😂

[@harshit7787]

🖕🙂

[@prachisingh6658]

Same to u bro

[@SuryaChakraborty-fw1zw]

Same to u🤢

[@poonamSinghaniya-j9z]

Same to you

[@anshu.6663]

Tomorrow is my preboard ....and really it is very helpful for me 😍😍😍

[@paidfire69]

Me too bro

[@Raagni-cz2of]

Tmrw exams hai me aaj syllabus pura krni baithi hu with the help of physics wallah ppl. It's been 11 50 night aur I have to complete still 10 chapters so I have to hear classes until 5😅

[@vidhi_chauhan31]

Hogyi preparation?

[@HUSTLER0.1]

Anyone day before exam

[@soumyaswain5210]

Imagine u r the topper of class 10 in INDIA Now. Remember the first word😂😂

[@RajKumarrapidovlogs2812]

Compartment ke paper ke upar video banaiye jo hum jaise bache clear kar sake jinke compartment aai ho or kaun kaun se chapter a sakte hain

[@sureshbhabla4456]

Thanku mam you are the best teacher 😊😊😊😊😊🥰 I am understanding each and every word wow ❤

[@Prince.157]

🤨

[@omprakashmyadav7281]

Mam matlab jo vegetarian hai unke pass jada joule ki energy hai as compare to non-vegetarian??

[@shrutisuteri2008]

Yes...

[@radhachauhan6400]

Kal science ka exam hai 2024😂 nam batate jana in reply 😂😂😂

[@gursewaksingh9449]

Yes

[@gursewaksingh9449]

Angad

[@dynamitegaming1758]

Priyam kumar

[@velocxty2477]

ABSOLUTELY INCREDIBLE explanation as always ma’am!😃👍💪⚡️

[@Mayankeditorxi]

Tomorrow is my exam🤣😔*RBSE*

[@not_decided2249]

Mera bhi

[@rambhadevi3814]

Watching just 4hr before exam😂🤭

[@adityayadav51915]

Hllo

[@adityayadav51915]

You looking cute......

[@rajnisharma878]

Today is my exam and I see this video at 6.30 am Please pray for me 🥺🥺🥺

[@roshniverma5276]

Same broo 🥲

[@rajnisharma878]

🥺🥺

[@Gaurav4152b]

All the best

[@King.ofarm_]

Today is my science paper and i am watching it at 12.30am

[@pavimo3215]

Maine to bhai 4-5 baar revise kar lia Fir bhi lag raha hai kuch nahi aata

[@m_z_k.11]

​@@pavimo3215 😂

[@ayushhh0_0]

​@@pavimo3215 bhai physics nahi ati 💀

[@shafanshamshad9632]

Subhanallah subhanallah🤣🤣🤣👍👍👍

[@sunshine3179]

Ma'am please upload short video on control and coordination

[@harshitkanojiya3005]

Thanks for uploading concept mapping and revision because today is my pre board - thanks PW

[@kulvindersingh7481]

🌳-> 🦌-> salmon bhoi 🌚

[@asthakumari1315]

💀

[@KAMYA-z4q]

7 bje mera exam h can u assume that 6 bje vdo dekhi main ne ...but really dr lg rha h pre board h

[@Sanojkumar-bz9gk]

Thank you so much pw great teachers for your kind help of best quality education in one shot short lecture 🙏🙏🙏

[@harshu4427]

Watching last day before exam 🥲

[@youtubesb5674]

Same 😫

[@officialmr.Y]

But mera revision chl rh ahai

[@youtubesb5674]

@@officialmr.Y 🥲

[@harshu4427]

@@officialmr.Y acha badiya

[@satyam-785]

Tomorrow is my pre board and I watch this chapter 🤣🤣😅

[@SaritaSingh-fz9mq]

Me also 😂

[@payalyadav7143]

Me also

[@bravemasterop6159]

@@payalyadav7143 hlo

[@Artworld_1210]

Samridhi mam is a great biology teacher luv ❤u mam 😊

[@NidhiKumari-rq4tg]

One last time visiting to this video Miss u a lot ma'am Those evergreen memories of live classes in batch are just unforgettable!!!!

[@Kumar-wj4rt]

Shi kha Aap ne😔 All the best exam 👍

[@Yashashvi_Dave]

Really really helpful I will diffently recommend this to my friends

[@asthasrivastava8812]

really, my biology was completely ready through you videos...desperately searching for marathon classes but got even better ones!

[@shilpibarnwal9666]

Same bro

[@harshbhatt9314]

Is this sufficient bro..!??🤕

[@dhirajshuklauuu877]

Hii astha

[@goutamsingh3155]

Hi

[@adityayadav51915]

Hllo

[@anuradhaqueen6479]

Mam is multi talented teacher and hum bahut lucky hai ki aap jaisi mam mili so , I'm lucky ❤❤❤😊

[@freefireasad]

Accha😂

[@schoolwork-le3go]

Mam if human being eat plant that place we are primary consumers than how only hetrotopic can a primary 😀😀

[@imHarsh_07]

Herbivores mam ne bola tha

[@schoolwork-le3go]

@@imHarsh_07ham herbivores ha ya omnivores 😀

[@imHarsh_07]

@@schoolwork-le3go omnivores

[@smartyboysofficial]

LEGEND ARE WACTING IN BEFORE ONE DAY OF EXAM 😂❤️

[@AmanGupta-yh8pe]

😁😁

[@ishika6028]

Clssess ke lecture se jda PW ke lecture smj aate hh

[@rehanbatt01]

😂

[@gamecrusher4996]

Brother / sister stop wasting time by reading coments Focus on video 😂

[@Priti62060]

Thanku mam mujhe aapne mummy aur papa ka sapana pura karna hai

[@princebhaisora6288]

Accha... Good🌸

[@GHULEFF]

God give all student above 90% above

[@Abhishek_gupta1729]

SCIENCE BLUEPRINTS CHEMISTRY :- CHAPTER 1. - CHEMICAL REACTIONS AND EQUATIONS ( 6 MARKS ) CHAPTER 2 - ACID BASES AND SALTS ( 3 MARKS CHAPTER 3 - METALS AND NON METALS ( 10 MARKS ) CHAPTER 4 - CARBON AND ITS COMPOUND ( 6 MARKS ) TOTAL - 6+3+10+6 = 25 BIOLOGY :- CHAPTER 6 - LIFE PROCESSES ( 9 MARKS ) CHAPTER 7 - CONTROL AND COORDINATION ( 3 MARKS) CHAPTER 8 - HOW DO ORGANISMS REPRODUCE ( 6 MARKS CHAPTER 9 - HERIDITY ( 7 MARKS) CHALTER 15 - OUR ENVIRONMENT ( 5 MARKS) TOTAL 9+3+6+7+5 = 30 PHYSICS :- CHAPTER 10 - LIGHT REFLECTION AND REFRACTION ( 10 MARKS) CHAPTER 11 - HIMAN EYE AND COLOURFUL WORLD ( 2 MARKS) CHAPTER 12 - ELECTRICITY ( 7 MARKS) CHAPTER 13 - MAGNETIC EFFECTS OF ELECTRIC CURRENT ( 6 MARKS). TOTAL - 10+2+7+6 = 25

[@Ensoxharshh]

Yeh to kahi given nahi hai

[@Ensoxharshh]

Yeh to kahi given nahi hai

[@aarushidwivedi9716]

This is not true, bio -27 Physics - 26 Chemistry-27

[@rii007]

@@aarushidwivedi9716 ek marks kaha gya.... 79 hi total ho rha hai

[@tanishapunia7531]

@@rii007 80 he hai total

[@asiadebbarma6878]

Bro meri halat to tide ho Rahi hain 🤣board bhi start hone wala hain 😹

[@tarunyadav-mk2zs]

20:17 comment Kiya padhne aaye ho padlo

[@criclights18]

Mam is telling that primary consumer is always a herbivores animal but why not a omnivorous can be a primary consumer 😊

[@xzrnl__tr]

I hope everyone achieves good mark in comp

[@swadhinsproediting9029]

All the best for tomorrow science exam 😂😂

[@Riyazmusa444]

Aaj hi ha yarrrr😢

[@Ya_x_h]

Thanku broo 😭😂

[@parultyagi9738]

Very useful and excellent explaination