关于后谓语动词用单数还是负数的

第一个问题用单数是很明显的.
现在来说一说你提到的这些词被and连接时的用法：every...and(every)...; each...and(each)...;no...and(no)...; many a ...and(many a )...连接两个单数名词做主语时,谓语用单数形式,如：Many a boy and (many a ) girl has made the same mistake.
many a 表示复数含义,但做主语时,后谓语仍然用单数.
当连接的两个词指同一个人、同一事物或同一概念和一整套器具的时候,也用单数.如:
A ford and knife is used by westerners.
The doctor and professor is coming at once.