单选题：Some of you may have finished Unit One. ____, you can go on..

Sailing down the Yellow River,______. A. the boat hits a rock B. an accident had happened C. the boat hit a rock D. a terrible accident happened

We all know that, _____ , the situation will get worse[ ]A. if not carefully dealt with B. not if dealt carefully withC. if don't deal with carefullyD. not if carefully dealt with

You may depend on ______ that I shall always help you .[ ]A. thisB. it C. thoseD. one

Didn't _________ ever occur to you that such possibilities still existed? [ ]A. they B. itC. thatD. this

Did you find____impossible for him to tell the truth? [ ]A. this B. itC. thatD. what