________ it is, the boy never seems to be able to finish it off.

A．However interesting a book

B．Whatever interesting a book

C．How interesting a book

D．What an interesting book

中国外汇交易中心在上海、北京双中心异地备份体系结构的基础上，发展为（）的容灾系统。

A.两地一中心

B.两地两中心

C.两地三中心

D.三地两中心