俗话说：水缸“穿裙子“，天就要下雨．水缸“穿裙子“是指：盛有水的缸的外表面，齐着水面所在位置往下，出现了一层均匀分布的小水珠。关于出现小水珠的原因，下列说法中正确的是[ ]

A．水缸壁有缝隙，水渗了出来

B．是水的蒸发现象

C．是扩散现象

D．是水蒸气的液化现象

Serialization delay and (71) delay are the two components of network delay that are improved by increasing bandwidth. Serialization delay, i.e. the amount of time it takes to put the (72) on the wire, and queuing delay (depth of the queue) are improved by increasing the (73) from a 128Kbps circuit to a T1. However, three other components of delay, routing/switching deiay, distance delay, and protocol delay are components that can not be positively affected by an (74) in bandwidth. If the circuits are not over-utilized, then increasing the bandwidth to improve the (75) of the application will only result in an increased bandwidth with no positive effects on performance.

（74）是（）

A.increase

B.decrease

C.maintenance

D.extension