他们在外面玩的时候，下起了雨。
It started raining while they were playing outside.
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while英 /waɪl/|美 /waɪl/
They英 /ðeɪ/|美 /ðeɪ/
were英 /wɜː/|美 /wər/
playing英 /ˈpleɪɪŋ/|美 /ˈpleɪɪŋ/
解释
while 引导时间状语从句，从句中用过去进行时 (were playing) 描述正在进行的背景动作。
It started raining while they were playing outside.
while 引导时间状语从句，从句中用过去进行时 (were playing) 描述正在进行的背景动作。