【题目】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 driving
B. must have been driving
C. could have driven
D. would have driven
在线课程【答案】 B
【解析】
试题分析：考查句意理解。must表推测，对过去正在进行的动作的推测。故选B。