关于CHAP的设置,下面说法正确的是()
A. CHAP=2,表示Immediate Assignment on TCH, SDCCH Chosen First
B. 如果CHAP=2,则在立即支配过程中永远不会占用SDCCH
C. 如何为短消息业务,不管CHAP设为1还是2,均不会立即指配到TCH上
D. CHAP=3,表示Immediate Assignment on TCH, TCH Chosen First, GSM Phase 2 Mobiles, "Channel Needed" Supported