— He hardly spent any time on his subjects, _____?    

— _____, so he does badly in his lessons. [ ]

A. didn't he; Yes

B. did he; Yes

C. didn't he; No

D. did he; No

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.

（71）是（）

A.buffering

B.queuing

C.receiving

D.timing