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.

59（）

A．transmitting devices

B．transmitted devices

C．receiving devices

D．received devices

适宜用于化学法测定蛋白质的尿液pH值为

A．1～3

B．2～4

C．5～7

D．7～9

E．8～10