第3题: [单项选择]Rarely ______ left alone together for any length of time, but one thing now seemed certain. A. they were B. were they C. had they been D. they had been 参考答案:C 答案解析:该题中包含否定副词rarely,且该词置于句首,因此要引起所在小句谓语动词的部分倒装,根据后面but分句用的过去时参照,推出rarely分句中的动词应该用过去完成时。