I was on the highway when this car went past followed by a police car. They at least 150 kilometers an hour.
A. should have been doing
B. must have been doing
C. could have done
D. would have done
网友回答
A. should have been doing
(答案→)B. must have been doing
C. could have done
D. would have done
解析：must表推测，对过去正在进行的动作的推测。