Both of them can make fruit salad,____ ____?(改为反意疑问句)

问题描述:

Both of them can make fruit salad,____ ____?(改为反意疑问句)
我知道答案是can`t they,但是为什么要填他们呢?

存在情态动词,助动词时,反义疑问句对情态动词、助动词否定.比如你这道题.
只有动词时,就对该动词对应的助动词提问.比如:You like him,don't you?(like 对应的是do )
He likes her,does he?(likes 对应 does)