Theboywassittingunderanappletree       anapplefellontoh...

问题详情：

The boy was sitting under an apple tree        an apple fell onto his head.

A. when             B. while                    C. after

【回答】

A。引导表示短暂*动作的时间状语从句应用when; while表示动作或状态的延续；after意思不符合题意。故选A。

知识点：连词

题型：选择题