—I visited France last year. —Thatinteresting.A. wasB. can be C. must beD. must have been

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A. was
B. can be
C. must be
(答案→)D. must have been
解析：考察情态动词用法。情态动词+have done表示对过去事实的推测，根据本题第一句话visited可知是过去时，那么是过去情况进行推测，故使用情态动词+have done。故D正确。