下列叙述中正确的是（  ）
Which of the following statements are correct?  
A.在TD-SCDMA系统中每20MS为一个无线帧
In the TD-SCDMA system, every 20ms forms a radio frame
B.在TD-SCDMA系统中每10MS为一个无线帧
In the TD-SCDMA system, every 10ms forms a radio frame
C.每个无线帧可以分成2个子帧
Each radio frame is divided into 2 subframes
D.每个无线帧可以分成4个子帧
Each radio frame is divided into 4 subframes