Close the windows well before going to bed.为什么before后要跟动词ing形式?

We must keep all the windows -----.A close B closed We must close the windows when we leave.(同义句)We must____ the windows ______when we leave. we could close all the windows when we are using the air conditioner. we cantn`t close all the windows when we are using the air conditioner. Did you close all the windows? close the windows,tom.改成否定句 we often keep the windows of our office ____.a.closing b.close c.opened d.closed It was windy outside yesterday.We had to keep the windows __(close) that day.为什么不能填closing. It's windy today.We must keep the windows _____.A.close B.to close C.closing D.closed要有解析,最好能详细点. ---------(close)the windows before you leave the classrom. Before you leave the classroom,please r____to close the windows. L ook The wind is getting ______ to us.Oh We should keep all the windows and doors ______.Aclose,closed B.close ,close C.closed,open D.close,open Keep the windows ________(close).It's too cold today. Don’t forget _________(close) the windows after school. 连词成句windows,doors,close,and,the Be ----to close the windows before you leave. I____(close)the windows before I leave.动词填空 Don't f___ to close the windows after school,class