二尖瓣前叶M型曲线，曲线达E峰后，随后迅速下降，下降速度正常为（）

A.120～160cm/s

B.100～140cm/s

C.80～120cm/s

D.60～100cm/s

E.40～80cm/s

In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the ______ between sending the notification and notification arriving at the source, thousands of additional ______ may arrive. In ATM network, a major tool for preventing ______ is ______ control. When a host wants a new virtual ______, it must describe the traffic to be offered and the service expected.

A．interval
B．time
C．slot
D．delay