英语题please close the door and windows when you _____the office

英语题please close the door and windows when you _____the office
please close the door and windows when you _____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.leaving
if 后跟动词一般现在时