With his attention ___ on the book he was reading ,he didn't notice what had happened.

问题描述:

With his attention ___ on the book he was reading ,he didn't notice what had happened.
With his attention __ on the book he was reading ,he didn't notice what had happened.
A.focuses
B.focused
C.to focus
D.focusing
为什么?
请详细说明每个选项.

with复合结构的用法.with+N.+Ving/Ved/to do
名词与动词是主动时Ving.
与动词是被动时Ved.
表示将来的动作时to do
focus one attention on sth.
attention 与focus 是被动关系.