TD—SCDMA物理信道的结构可分为哪几层？（）
A.超帧
B.无线帧
C.子帧
D.时隙/码道
参考答案：A, B, C, D
70. I know it is difficult __________ him to talk like the lecturer, but I think he should grasp every chance .
A．of
B．for
C．with
D．Over
车辆行驶中每次观察后视镜间隔时间不得超过（）秒。.
A.20
B.30
C.60
