--- By the way, how much _______ the glasses?  

--- The glasses? Oh, _______ 230yuan. [ ]

A．is, it's          

B．are, they're  

C．are, it's      

D．is, they're

（）用于净空受限制的地下电气化线路。

A、柔性悬挂

B、刚性接触悬挂

C、两者都是

D、都不是