do not forget to turn off the lights before leaving the room 为什么是leaving 不是leave

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do not forget to turn off the lights before leaving the room 为什么是leaving 不是leave
do not forget to turn off the lights before leaving the room 为什么是leaving 不是leave

do not forget to turn off the lights before leaving the room 为什么是leaving 不是leave
before doing sth 固定搭配
LS说的也很对,再举个例子
1.We must have a plan before doing any work.
做任何工作前,我们必须订好计划.

before 为介词 后接动名词即V-ing

before 是介词,后加doing

before是介词,介词后面接名词 或表名词词性的词 。leave+ing 表名词词性。
如果后面接的是一个句子,可以考虑用动词的时态。

按理说此题应该是考察知识点Why don't you = Why not,注意Why not不能Why don't you turn off the lights before leaving the classroom?