Packet-switching wireless networks are preferable (71) when transmissions are (72) because of the way charges are (73) per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are (74) for the (75) of time they use the network.

A．computing

B．incurious

C．incurred

D．incurred

A点高程330.000m，B点高程230.000m，下列说法中的（）是错误的。

A.B点比A点高

B.A点比B点高

C.A-B的高差是100.000m

D.A-B的高差是－100.000m

E.A点到B点的坡度是10.0%