为什么 ten dollars is not enough 用is 应该10美元复数呀

为什么 ten dollars is not enough 用is 应该10美元复数呀 5 dollars is enough 为什么用is dollars 是复数啊 how much IS this pair of trousers ten dollars()enough 老师说用is twenty dollars is enough Two is enough ,为什么谓语动词用的是单数呢?而 Ten of them are teachers 却是复数 Is a hunderd dollars enough 为什么用IS,可否用Will be? This watch is not worth even ten dollars.中的worth 作什么成分,怎么用呢? enough is not enough ( ) Ten dollars enough three pairs.A.are,in B.is,for C.are,f 一个英语听力问题!：I only have ten dollars,is it enough for three tic 为什么港币上写的ten dollars?十美元吗? Two thousand dollars is enough for the car.此句里的be动词为什么用is而不是