点A与点B关于直线a对称，则直线a垂直线段AB，且平分线段AB。[ ]
正确
His brother ___ the Party about five years ago.
A．joined
B．joined in
C．has joined
D．has joined in
鼻咽癌患者远处转移，最常见的组织是（）。
A.骨
B.肺
C.肾
D.脑
E.肝脏
