We don’t permit _____in the classroom; that is to say, students aren’t  permitted _____in the classroom.[ ]

A. to smoke; to smoke          

B. smoking; smoking  

C. smoking; to smoke          

D. to smoke; smoking

小批试生产阶段的主要目的是（）

A.进行设计定型

B.收集用户意见

C.进行生产定型

D.进行模拟试验