Question

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

Answer 1

B

第一句話使用了一般過去時(shí)，由此可知第二句話是對(duì)過去事情的猜測，需用must have done.本題意為“我正在高速公路上行駛，這時(shí)一輛警車跟隨著著這輛車從旁邊經(jīng)過。它們一定是以至少每小時(shí)150公里的速度行駛。”故選B。A項(xiàng)表示“本應(yīng)該……”，C項(xiàng)表示“本能夠……”不合題意。