With his attention on his book, he didn’t notice someone entering his room.
A. concentrating
B. concentrated
C. to concentrate
D. concentrates
网友回答
A. concentrating
(答案→)B. concentrated
C. to concentrate
D. concentrates
解析：考查非谓语动词。with+名词+doing/done构成复合结构，attention与concentrate是动宾关系，即“集中注意力”，应该用过去分词，排除A；with后不能用动词原形或三单，排除D；句意：由于注意力在他的书上，他没有注意到有人进入他的房间。根据句意可知，是已经发生的事情，动词不定式表将来，排除C。故选B。