The book _____ he bought yesterday is very interesting .A./ B.why C.when D.whatThe book _____ he bought yesterday is very interesting .A./ B.why C.when D.what

The book _____ he bought yesterday is very interesting .A./ B.why C.when D.what
The book _____ he bought yesterday is very interesting .
A./ B.why C.when D.what

选择A
The book he bought yesterday is very interesting
他昨天买的书很有趣.
he~是book的定语从句.相当于which he bought,当关系代词在定语从句中作宾语时,可以省去