---The dustbins ______ for three weeks．---In fact, they ______ once a week．A.haven't emptied; should have been emptiedB.haven't been emptied; should be emptiedC.haven't been emptied; should have emptiedD.haven't emptied; should have emptied
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B解析根据句意，第一个空应该用现在完成时态的被动语态；第二个空为情态动词的被动语态。