— I don't think teenagers should drive cars. 

— ____. They aren't serious enough. [ ]

A. I agree

B. I don't agree

C. I think

D. I don't think

下列何药在妊娠期应用时危险性分类为D类？（）

A.青霉素

B.阿奇霉素

C.头孢哌酮

D.四环素