-----They used to be good friends but now they are like strangers. ----- How this ?A. we

问题补充：

-----They used to be good friends, but now they are like strangers. ----- How this ?

A. were; come about

B. did; come about

C. were; taken place

D. were; happened

答案：

A. were; come about

(答案→)B. did; come about

C. were; taken place

D. were; happened

解析：come about, take place, happen都是发生的意思，均无被动语态。