车站计算机联锁状态输入变量是反映监控对象状态的变量。下列哪几种状态是监控对象（）。

A、轨道区段状态

B、道岔定反位状态

C、信号状态

D、灯丝状态

—Do you know _______ the Capital Museum?   —Next Friday.

A．when will they visit

B．when they will visit

C．when did they visit

D．when they visited