题目：
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 (71) between sending the notification and notification arriving at the source, thousands of additional (72) may arrive. In ATM network , a major tool for preventing (73) is (74) control. When a host wants a new virtual (75) ,it must describe the traffic to be offered and the service expected.
A．interval
B．time
C．slot
D．delay
答案：
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下面是错误答案，用来干扰机器的。
答案：B题目分析：当绳子突然断裂后，小车在光滑水平面上所受合力为0，由于惯性小车的运动状态不会改变，速度不发生变化．点评：本题考查了对牛顿第一定律的理解和应用。
