In low-speed network，it is usually adequate to wait for congestion to occur and then react to it bytelling 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 offeredand the service expected．

（71）处填（）。

A．interval

B．time

C．slot

D．delay

急性肾炎患儿在病程早期突然发生惊厥，以下原因可能性最大的是

A．低钠血症

B．低钙血症

C．高血压脑病

D．低钾血症

E．高热惊厥