以下( )元素在脑中含量升高是诱发老年性痴呆的危险因素。
A．钠 B．铝C．锌 D．硒
参考答案：B
My brother is good at chess and he joined the Chess Club ______ June, 2012.
A．on
B．in
C．at
D．to
外加电流阴极保护法
