A．They focus on the issue of making friends.
B．They help people who are especially lonely.
C．They are the most classic books on the same topic.
D．They teach people how to be popular in a group.

A．By talking to people.
B．By current friends' introduction.
C．By searching for people having the same interests.
D．By developing new hobbies.

A．There are lots of people getting online every day.
B．Lots of people in your area want to know you.
C．You can get to know another person instantly.
D．You will not judge a person by his appearance.