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 (64) between sending the notification and notification arriving at the source, thousands of additional (65) may arrive. In ATM network , a major tool for pre- venting (66) is (67) control. When a host wants a new virtual (68) , it must describe the traffic to be offered and the service expected.

64（）

A．interval

B．time

C．slot

D．delay

女孩，8岁，小学二年级，到某保健中心查体。

该年龄期最突出的特征是（）。

A.体格生长速度相对缓慢

B.智力发育突出，可接受系统教育

C.除生殖系统外，各系统器官外形接近成人

D.感染性疾病发病率下降

E.易发生屈光不正、龋齿