MYT40型1211灭火器的灭火射程在（）m。

A、3～5

B、7～8

C、8～9

D、6～8

In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

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 (1) between sending the notification and notification arriving at the source, thousands of additional (2) may arrive. In ATM network, a major tool for preventing (3) is (4) control. When a host wants a new virtual (5) , it must describe the traffic to be offered and the service expected.

2（）

A．packets

B．cells

C．message

D．files