—Sorry, I’m late.____ the film____?

—Yes.It__________ for half an hour.

A．Did; begin; has begun

B．Did; begin; has been on

C．Has; begun; has begun

D．Has; begun; has been on

用硫酸酸洗时，约有（）的氧化铁皮是由于机械剥离作用除去的。

A.35％

B.58％

C.78％

D.90％