You all those calculations! We have a puter to do that sort of thing.
A. needn’t have done
B. must not have done
C. shouldn’t have done
D. can not have done
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(答案→)A. needn’t have done
B. must not have done
C. shouldn’t have done
D. can not have done
解析：情态动词用法。A本不需要做某事却做了；不存在B这个结构；C本不应该做某事却做了。D不可能做了某事。句意：你本不需要做所有的计算。我们有计算机做这样的事情。