--- When can I see the doctor, madam?

--- Let me see. Sorry, you ___________ your turn, so you will have to wait again.

A．are missing

B．have missed

C．will miss

D．missed

测试自动喷水灭火系统的湿式报警阀的排水管路时，发现水力警铃长时间不响，可能存在的原因是（）。

A、报警阀管路堵塞

B、报警管路阀门关闭

C、水力警铃损坏

D、报警阀后压力大于阀前压力。