一、二级视频会议保障率指标属（）类指标。
A.通信规模
B.通信运行
C.通信服务能力
D.通信管理
参考答案：B
（x2﹣xy+y）﹣3（x2+xy﹣2y）
You had better________ some time every day for sports so that you can keep yourself energetic.
A．set aside
B．take up
C．put away
D．give out
