The machine has been used many years_____ it doesn’t work well occasionally.

A．That’s because

B．It’s no wonder that

C．There’s no doubt if

D．It’s unlikely that

特高压并联电抗器采用铁芯式结构，铁芯由（）组成。

A.铁芯柱

B.铁轭

C.引线

D.套管