线阵天线安装需要保证阵与阵之间的间距（最小距离）为（）米以上。
A.2
B.3
C.4
D.5
参考答案：A
Peter was so excited _____he received an invitation from his friend to visit Wuxi.
A．where
B．that
C．why
D．when
根据BS7799的规定，访问控制机制在信息安全保障体系中属于（）环节。
A、保护
B、检测
C、响应
D、恢复
