中继站可以采用定向天线。（）
参考答案：错
His sister has recently got engaged ____ a foreign teacher, who has engaged ____ education research for years.
A．with; in
B．to; in
C．with; on
D．in; for
强碱阴树脂的失效点是什么？强碱阴树脂在什么条件下能去除硅酸？
