通常情况下，载体应连接多少个以上半抗原才能使动物有效产生抗体（）
A.25个
B.20个
C.35个
D.30个
E.15个
参考答案：B
A new supermarket __________ in my hometown last month.[ ]
A. built
B. has built
C. was built
D. is building
碘过量可导致甲状腺肿。
