Packet switching is a method of slicing（71) messages into parcels called "packets," sendin

Packet switching is a method of slicing(71) messages into parcels called "packets," sending the packets along different communication(72) as they become available, and then reassembling the packets(73) they arrive at their destination. Prior to the development of packet switching, early computer networks used leased, dedicated telephone circuits to(74) with terminals and other computers. In circuit-switched networks such as the telephone system, a complete point-to-point(75) is put together, and then communication can proceed.

A．binary

B．useful

C．digital

D．analog