The（）is a collection of computers connected together by phone lines that allows for the global sharing of information.

单项选择题（）is the sending and receiving of the messages by computer. It is a fast, low-cost way of communicating worldwide.

A．LAN
B．Post office
C．E-Mail
D．Interface

单项选择题（）is not a linear structure.

A．Graph
B．Queue
C．Stack
D．1-dimension array