连续信源和离散信源都具有可加性。

Many children use the Internet to get useful knowledge and information, and to relax in their free time. But some of them are not using in a good way. Here are some rules to make sure you are safe and have fun on the Internet.
● Make rules for Internet use with your parents. For example, when you can go online, for how long and what activities you can go online.
● Don’t give your password (密码) to anyone else, and never leak out the following information---your real name, home address, age, school, phone number or other personal information. 
● Check with your parents before giving out a credit (信用) card number.
● Never send a photo of yourself to someone in e-mail unless your parents say it’s OK.
● Check with your parents before going into a chat room. Different chat rooms have different rules and attract different kinds of people. You and your parents must make sure it’s a right place for you.
● Never agree to meet someone you met on the Internet without your parent’s permission (允许). Never meet anyone you met on line alone.
● Always remember that people online may not be who they say they are. Treat everyone online as strangers.
● If something you see or read online makes you uncomfortable, leave the site. Tell a parent or teacher right away.
● Treat other people as you’d like to be treated. Never use bad language.
● Remember—not everything you read on the Internet is true.
小题1: If you want a true friend on the Internet , you can ____________ .
A  tell the people what your name is .      B  meet the people on line alone.
C  write an e-mail about yourself .        D  get your parent’s permission.
小题2:It’s good for children to ________ on the Internet.

A．give password to others	B．get useful knowledge and information
C．give out a credit card number	D．go into a chat room as they’d like to

小题3: The underlined phrase “leak out” in the third paragraph may mean “________.”

A．give away

B．leave out

C．give out

D．put away

小题4:If your parents don’t agree, never ________.

A．read anything on the Internet	B．relax in your free time
C．have a face-to face meeting with anyone you met online
D．treat other people as you’d like to be treated

小题5: This passage is mainly about “________”.

A．How to use Computers	B．Surfing on the Internet
C．Information on the Internet	D．Internet Safety Rules