The workers busily when the boss came to look for something she in the office.
A. had worked; had left
B. were working; had left
C. working; had left
D. had worked; left
网友回答
A. had worked; had left
(答案→)B. were working; had left
C. working; had left
D. had worked; left
解析：从句when the boss… 给出了内容是句子的重心, 主句用了过去进行时交代背景,因为从句和内容重要,这里的when译成 “”这时”.