While Jim the floor, someone at the door.
A. was sweeping, was knocking
B. was sweeping, knocked
C. swept ,was knocking
D. swept, knocked
网友回答
A. was sweeping, was knocking
(答案→)B. was sweeping, knocked
C. swept ,was knocking
D. swept, knocked
解析：while引导的从句一般用进行时态，而主句为一般时态，故选答案为B