简述程控交换机的容量指标。
参考答案：
A．远处学生听到的声音响度大
B．年段长出的声音音色不好
C．年段长发出的声音音调低
D．远处学生听到的声音响度小
—Can we swim in the river?
—No. My parents told me ________ here.It's dangerous. [ ]
A. to swim
B. not to swim
C. don't swim
D. swim
