Option D is correct because ‘recollect’ means ‘remember’. Amit could not remember the incident that happened in his childhood. Thus option D is the appropriate word most similar in meaning for the given sentence.
Option A is incorrect because ’assemble’ means ‘to gather’. Thus, option A is not the appropriate word most similar in meaning for the given sentence.
Option B is incorrect because ‘realize’ means ‘to come to know’. Thus, option B is not the appropriate word most similar in meaning for the given sentence.
Option C is incorrect because ‘memorize’ means ‘to learn and remember exactly’. Thus, option C is not the appropriate word most similar in meaning for the given sentence.