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
若M是ⅡA族的某元素，则与M同周期且相邻的元素不可能位于元素周期表的
A．ⅠA
B．ⅠB
C．ⅢA
D．ⅢB
There is no way to get to the small island where my grandparents live _____ by boating. [ ]
A. rather than
B. other than
C. instead of
D. in place of
