B.呼叫可以通过Normal Assignment 过程从TCH被分配到SDCCH
C.在Normal Assignment 中, 如果Physical Context Request 过程不成功呼叫就无法进行下去
D.同步切换比异步快
A.SDCCH not available, TCH not available
B.SDCCH not available, TCH available
C.SDCCH available, TCH not available
D.SDCCH available, TCH available