阅读下面的短文，并将答案写在答卷上。
Chat rooms and messaging can be great fun，but remember, you never really know who you are talking to online．It could be someone trying to trick you，some kind of weirdo（古怪的人），or someone really dangerous．Here are some tips to help you keep safe：
● Never use your real name in chat rooms—pick a special online nickname．
● Never tell anyone personal things about yourself or your family—like your address or telephone number ，or the school or clubs you go to．That goes for sending them photos as well. Remember, even if somebody tells you about themselves，never tell them things about you.
● If you want to meet someone you’ve only spoken to once, remember that they might not be who they said they were. Only meet people in public places and take along an adult—they should do this too，because they don’t know who you really are either!
● Never respond to nasty（淫秽的）or rude messages，and never send any either! If you feel suspicious or uncomfortable about the way a conversation is going，or if it’s getting really personal，save a record of it and stop the conversation．That way you can show someone and ask what they think．
● Be careful with any email attachments（附件）or links that people send you，they might contain nasty images，or computer “viruses” that could ruin your PC．So if _______ who it’s from，don’t open it．
小题1:What is the best title of the passage?（Please answer within 10 words）
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小题2:Which sentence in the passage can be replaced by the following one?
The person you are talking to online may mean to do harm to you．
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小题3:Please fill in the blank in the last paragraph with proper words or phrases to complete the sentence．（Please answer within 4 words．）
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小题4:Which of the suggestions do you think is the best for you? Why?（Please answer within 30 words．）
小题5:Translate the underlined sentence in the third tip into Chinese．
的公差是（）mm。