What kind of people think Internet addiction is not a real problem?
A. Those who have Internet addiction.
B. Those who have a weak personality.
C. Those who can well manage their time spent online.
D. Those who think the Internet is very powerful and useful.
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Which of the following is not mentioned as a circumstance under which endorphins may be released?
A. When we are reading an e-book.
B. When we have won a game.
C. When we have solved a difficult problem.
D. When we are instant-messaging our friends.
What can we learn about endorphins and Internet addicts from the text?
A. Endorphins are the essential brain chemicals that cause Internet addictions.
B. Endorphins can provide useful, real-life awards, which can help prevent Internet addiction.
C. Endorphins can encourage Internet addicts to talk and spend time with their family and friends.
D. Endorphins may be released continuously and for a long time in the brains of Internet addicts.
What is the author’s main purpose in writing the text?
A. To explain the causes of Internet addiction.
B. To analyze the advantages of the Internet.
C. To advise students to use the Internet wisely.
D. To discuss the impact of Internet addiction.
盒中有黄白两种颜色的乒乓球，黄色球7个，其中4个是新球；白色球5个，其中4个是新球。现从中任取一球是新球，它是白球的概率为（ ）（答案用小数表示）
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