主语是when and where,谓语动词用单数还是复数?为什么?

放在句首的并不一定就是主语.用when and where开头的句子,真正的主语是when and where之后的助动词(或情态动词或be动词)再后的成份.所以,谓语动词用单数还是复数,取决于助动词(或情态动词或be动词)再后的成份,即主语.
如When and where does he join the Young Pioneers?他是何时何地加入少先队的?此句,主语是he,不是when and where.when and where是副词,分别作时间和地点状语.由于he是单数,所以用且动词does.
再如,When and where were they playing games?他们是何时何地玩游戏来着?they是主语,所以用were.