Is a hunderd dollars enough 为什么用IS,可否用Will be?

Is a hunderd dollars enough 为什么用IS,可否用Will be? Forty dollars is enough for a child中为什么be要选择is呢? 5 dollars is enough 为什么用is dollars 是复数啊 Two thousand dollars is enough for the car.此句里的be动词为什么用is而不是 为什么 ten dollars is not enough 用is 应该10美元复数呀 twenty dollars is enough Ten dollars will be ( ) enough.A.quite.B how much IS this pair of trousers ten dollars()enough 老师说用is Here is a hundred of dollars.这里为什么要用is啊? Here () two dollars. be动词用are还是is? 主谓一致 twenty dollars is enough It is not yet a hunderd years old.