原句子是正确的吗？应该是He

must

stayed

up

last

night,didn't

he?

must表示推测时，反义疑问句和后面该有的助动词一致，题中行为动词就是didn't，must表示必须时，用musn't，不会用到needn't，除非是

Must

I

go

now?

No,you

needn't