— The terrible accident is under investigation— Actually, quicker action those workers t

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A. might have saved
B. must have saved
C. should have saved
(答案→)D. could have saved
解析：考查情态动词及虚拟语气。might have done 对过去可能性的推测，must have done对过去肯定的推测，should have done本应该做某事，实际上没有做，could have done本可以做某事，实际上没做，根据句意更快的行动本可以救那些困在矿中的工人的。所以选D。