Advanced set theory, every subset of countable set is countable

[@sachinhanchinamani9809]

What is mean by indexing set

[@adityakumarsingh8577]

aawaz nhi aa rha

[@HomelyQuiz_officialchannel]

Sir if we write this solution in bsc 2nd sem exam can we get a marks or not sir?????????

[@Naseer-786]

Think uu bhi