— Hey! Don't you remember me?

— Wow! Mary? You _____ curly hair. But now you have straight hair. [ ]

A. used to have

B. were used to have

C. are used to having

汽车主减速器锥齿轮目前常用渗碳合金钢制造，主要有20CrMnTi、20MnVB、20MnTiB、22CrNiMo16SiMn2WMoV等。