All

All _____ we need is enough rest after long hours' work. A. the thing B. that C. what D. which
答案是B,请问A为什么不能选?

B. that 是对的.
首先理清句子的结构,主句为All is enough rest ...,而（that）we need是定语从句,修饰all的,that是关系代词,在定语从句里做宾语,故还可以省去.
all the thing的话,thing要用复数things,而且后面的谓语动词也不能用is,要用are了.

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