问题

I was on the highway _______ this car went past followed by a police carThey ______ at least 150 kilometers an hour
A:when; should have been driving
B:while; would have driven
C:as; could have driven
D:when; must have been driving
B:while; would have driven
C:as; could have driven
D:when; must have been driving
正确答案是: