Question

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

A．when

B．while

C．then

D．as

Answer 1

A

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。