— I’ve been trying to call my Mom and Dad for almost an hour but_______________.— They

— I’ve been trying to call my Mom and Dad for almost an hour, but_______________.

— They must have hung up the phone improperly.

A. the line is always busy

B. the line is always taken

C. the phone is always busy

D. the phone is always used

请帮忙给出正确答案和分析，谢谢！