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.
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.
答
focus 是用来修饰 attention的，因为如果是人focus，那就用原型，可是这里是attention 被focus，所以用被动语态。
答
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.