He had been so absorbed watching the car passing by that he didn’t notice his friends .A.

问题补充：

He had been so absorbed watching the car passing by that he didn’t notice his friends .

A. to; coming

B. in; to come

C. on; coming

D. in; coming

答案：

A. to; coming

B. in; to come

C. on; coming

(答案→)D. in; coming

解析：考查固定结构。Be absorbed in doing sth，全神贯注于……；notice sb doing sth.注意到某人正在做某事。所以选D。