---I rang you yesterday afternoon. A man answered, but I didn’t recognize the voice.

--- Oh, it ____ my uncle. He was in my room then.

A．must have been

B．should have been

C．must be

D．should be

某探头有6个接线端，其接线端子的种类是（）

A.1对接报警线，1对接常开线，1对接常闭线

B.1对接报警线，1对接电源线，1对接防拆线

C.可以只接1对报警线

D.必须全部接上线才能报警