neither nor谓语用单数？什么时候用复数？

Neither/nor and either/or are a special case. If two subjects are joined by or or nor, the verb should agree with the subject that is closer to it. 谓语跟最近的主语。最近的主语是单数，谓语就是单数；最近主语是复数，谓语就是复数。
例： Neither they nor I was the winner.

Neither I nor they were the winners.

Neither they nor he has a cat.
Neither he nor they have a cat.

neither... nor...连接主语时要注意就近原则，也就是谓语动词的单复数要由最靠近它的主语决定。
如：Neither he nor I am a student.
Neither I nor he is a student.

谓语跟最近的主语。最近的主语是单数，谓语就是单数；最近主语是复数，谓语就是复数

neither nor可单可复，根据语境吧，没有什么特殊限制