1．(北京卷)Once/If the damage is done, it will take many years for the farmland to recover.
2．It is a long time since they separated, but it won't be long before they meet again.
3．He was working in the study，while his wife was preparing dinner for him in the kitchen.
4．(2019·福州高中月考)Actually, though/although/while we've done a lot to develop a lowcarbon economy, it doesn't live up to our expectations.
5．Unless you change your mind，I won't be able to help you.
6．It was not until midnight that the noise of the street stopped.
7．Hardly had she had time to sit and have a rest when the phone rang again.
8．Whether she comes here or we go there，the topic of the discussion will remain unchanged.
9．No sooner had the bell rung than the students quieted down.
10．We will finish the work on time，whatever difficulties we meet.
