I was on the highway when this car went

问题选择题

I was on the highway when this car went past fol. Lowed 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

答案

第一句话使用了一般过去时，由此可知第二句话是对过去事情的猜测，需用must have done.本题意为“我正在高速公路上行驶，这时一辆警车跟随着着这辆车从旁边经过。它们一定是以至少每小时150公里的速度行驶。”故选B。A项表示“本应该……”，C项表示“本能够……”不合题意。