is this the reason ____at the meeting for his carelessness in his work?A he explainedb what he explainedc how he explainedd why he explained为什么不用D而用A
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A对.理由:先排除B.C.(明白吧？），D中，explain及物动词，得有宾语，但why是副词，不能做宾语，故错了．A中，省略了关系代词which/that．另外：这是定语从句．在定语从句中，当关系代词做宾语时，可以省略．