I was on the highway _______ this car went past followed by a police car. They ______ 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

当购买性支出增加时，政府对商品和劳务的需求（），社会总需求增长。

A.减小

B.增加

C.不变

D.不变或增加