Option A is the correct answer because it is clear from the sentence ‘Soon, exhausted we cut short the lesson and retreated to the institute’ that the writer and his friends were tired and needed to rest.
Option B is incorrect because from the sentence ‘The helmeted toddlers skimming around like small gnats were an embarrassing contrast to our clumsiness. But we ignored them firmly.’ It can be understood that they had no issues to be in the same place as toddlers. Thus, option B is not the right answer.