when 后加主语是跟动词ing还是动词原形

题目

when 后加主语是跟动词ing还是动词原形
please close the door and windows when _____the office.
A.leaving B.leave
When the gas ___very hot inside the rocket,it wil run out of the end of the rocket ,so it can make the rocket fly up into the sky.
A,become B.becomes C.became D.is becoming
We never let the lights on when _____the rooms.
A .leave B.leave
if 后跟动词一般现在时吗

答案