Are these books interesting Yes,__of them are interesting.( all both )

问题描述:

Are these books interesting Yes,__of them are interesting.( all both )

all为什么?these books 又不知道是两本还是三本或三本以上的虽然these不知道是两本还是三本或三本以上的,但是both是两个 而all 可以是2,3,4