英语翻译这题应该选哪个答案？The most destructive natural disaster,tsunami,

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再问： 这题应该选哪个答案？ The most destructive natural disaster, tsunami, came unexpectedly ________ they will always live in peace and comfort. A. after B while C where D when
再答： 答案是D when 译文：最具破坏力的自然灾害，海啸，突然降临，此时他们将永远活在静谧和安逸里。 感觉这个选择题有些怪，前半句是过去时，而后面的从句是将来时。时间跨度不好理解。