Flow control is a function that prevents network congestion by ensuring that (59) do not overwhelm (60) with data.

There are three commonly used methods for handling network congestion. (61) is used by network devices to temporarily store bursts of excess data in memory until they can be processed (62) are used by receiving devices to help prevent their buffers from overflowing. (63) is a flow-control scheme in which the source device requires an acknowledgment from the destination aider a certain number of packets have been transmitted.

60（）

A．transmitting devices

B．transmitted devices

C．receiving devices

D．received devices

颅面血管瘤主要临床症状或CT特点（）

A.面部血管痣、癫痫、脑萎缩

B.面部血管痣、癫痫、基底核钙化

C.面部血管痣、头痛、浅部曲线样钙化

D.面部血管痣、癫痫、大脑表浅部曲线样钙化

E.面部血管痣、癫痫、大脑深部钙化