I can hear the Browns phone bell ringing but no one is answering it; they be at home.A.

问题补充：

I can hear the Browns phone bell ringing but no one is answering it; they be at home.

A. would

B. might

C. needn

D. can

答案：

A. would

B. might

C. needn

(答案→)D. can

解析：can 用在否定句中表示推测。