A.10-7 B.10-6 C.10-5 D.10-4
A.恢复保持的呼叫 B.建立一个激活呼叫 C.两个呼叫进行交替 D.拆除保持的呼叫
A.890M――915M B.935M――960M C.875M――900M D.900M――925M
A.1个 B.2个 C.255个 D.任意个