A good talk and explanation, but I was both surprised and not at all surprised to see yet another native English speaker who doesn't quite hear or quite repeat correctly the Spanish occlusive D, as neither do they almost ever manage to produce its unvoiced equivalent, which is the Spanish T in all its positions. The English equivalent D and T are somewhat fricative or less occlusive, and while they also work in Spanish, phonetically, they are very prominent, being the main phonemes that native Spanish-speakers put on in order to imitate or joke about Anglo foreigners or tourists. This fully occlusive Spanish D can, however, be heard in ceratin varieties of English, for example in lower-class New York speech, presumably brought in by Italian immigrants (as in the series Friends' Joey's catch-phrase "How you doin'"). I'm afraid there are also a few holes in the above rule, as the Spanish G doesn't act quite like the others, remaining fricative after an L and other precedents. For example, if you start a phrase with "gato", or if it follows an N, as in "un gato", the G is indeed occlusive (a voiced stop), but when following an L, as in "el gato", it becomes fricative, just as when following any vowel.