Question

【题目】Newton was playing under an apple tree _______ an apple fell on his head.

A. until B. while C. when D. after

Answer 1

【答案】C

【解析】句意：当牛顿在树底下玩得时候，这时一个苹果落到了他的头上。这里是when引导的时间状语从句，这时的意思；A. until直到；B. while当……的时候；C. when当……的时候；D. after在……之后。根据题意，故选C。