I was reading attentively in my own room suddenly he knocked at the door. A. whenB. whil

问题补充：

I was reading attentively in my own room suddenly he knocked at the door.

A. when

B. while

C. then

D. as

答案：

(答案→)A. when

B. while

C. then

D. as

解析：词义辨析。When表示当……时候；while和as表示两个动作同时发生；then的意思是那时；然后。句意：当他突然敲门时，我这在自己的房间里认真的读书。动作有先后，故选A。