Did she read books? [ ]
A. No, she didn't.
B. No, he didn't.
C. Yes, I did.
答案:A
简述关税同盟效应
膜可以是()。
A.固态、液态或气态
B.对称的或非对称的
C.中性的或带电的
D.酸性的或碱性的