He didn’t wait even . . . . . . . minutes but started a lecture.

We need to understand the difference between 'few' and 'little'. 'Few' is used with countable nouns (things you can count individually), while 'little' is used with uncountable nouns (things you can't count individually).

In this sentence, we're talking about "minutes". Minutes are countable; you can have one minute, two minutes, three minutes, etc. Therefore, we need to use either 'few' or 'a few'.

'Few' vs. 'a few': 'Few' implies almost none or not enough. 'A few' implies a small number, but enough to be significant.

The sentence "He didn't wait even... minutes but started a lecture" suggests he waited for almost no time at all. This means 'few' fits the context best.

'A few' would mean he waited for a small number of minutes which does not fit the meaning of the sentence, because he started the lecture almost immediately without any significant waiting time.

'Little' and 'a little' are incorrect because they are used with uncountable nouns, and minutes are countable.