Last night on my way home I saw an old lady driving a BMW car at I thought was a dangerous

问题补充：

Last night on my way home I saw an old lady driving a BMW car at I thought was a dangerous speed.

A. that

B. which

C. what

D. how

答案：

A. that

B. which

(答案→)C. what

D. how

解析：考查名词性从句。从句中缺少主语，故用关系词what。句意：昨天晚上在我回家的路上，我看到一位老太太开了一辆宝马车，我认为是非常危险的速度。故C正确。