A．Costly.
B．Time-consuming.
C．Genuine.
D．Safe.

A．Leaving our personal information on the sites.
B．Sending out our information to a group.
C．Giving out the contact page to our target.
D．Copying the same words and sending them to all.

A．It makes contacts easier and quicker.
B．It booms business and economy.
C．It improves interpersonal relationship.
D．It saves people a lot of money.