— Got your driving license?

— No. I ________ too busy to have enough practice, so I didn't take the driving test last week.[ ]

A. was  

B. am

C. have been  

D. had been

可能产生有害污染物的保藏方式是（）。

A.辐照保藏法

B.微波杀菌法

C.高温灭菌法

D.发酵法

E.熏制法