----Have you finished the book ?--No I’ve read up to the children discover the secret

问题补充：

----Have you finished the book ?

----No, I’ve read up to the children discover the secret cave. .

A. which

B. what

C. that

D. where

答案：

A. which

B. what

C. that

(答案→)D. where

解析：句意：你看完了这本书了吗？还没有，我已经读到孩子们发现了秘密的山洞。where引导状语从句表示在哪个地方，故选D