I saw James doing his homework ____ I went to his room.

I saw James doing his homework ____ I went to his room.
A、that
B、when
C、how
D、which
【正确答案】：B
【题目解析】：此题考察when 引导的时间状语从句，表示”当“的意思，当我走进他的房间时，我看见他正在做作业。因此选B.