----What did the teacher say?

----She asked            .

A．what was the matter with you

B．what were you doing

C．where you have gone

D．where you have been

（）的铁心应采用硬磁材料。

A.电机

B.永久磁铁

C.变压器

D.继电器

E.录音磁带上的磁粉