I was on the highway when this car went past fllowed by a police car .

问题描述:

I was on the highway when this car went past fllowed by a police car .
They_____ at least 150 kilometers an hours.
A.should have been going B.must have been going
C.could have gone D.would have gone

选 B.must have been going
理由:上文提供了证据“I was on the highway when this car went past fllowed by a police car",即有把握的肯定推测,用must.因为是对过去某一时刻的推测,用过去完成进行时,have been going.