主语是when and where，谓语动词用单数还是复数？为什么？

when and where不可能是主语，因为它们是副词。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.

这个看后面的谓语动词后面的名词是单数还是复数了；
比如：后面名词是：schools,people,teachers；那么毫无疑问要用are或者were
翻译若是单数名词的话，就有is或者was

例句一：when and where were they playing basketball？谓语动词后面名词是复数they，所以要用were；
例句二：when and where does she come from?谓语动词后面名词是单数she，所以要用does；

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.

两个都可以引导主语从句，谓语动词用单数。一个句子做主语谓语用单数。