A micro blog with space for 140 Chinese characters had once been a source of endless amusement for Wang Ganghui, a senior majoring in biochemistry at Ji'nan University. Until last month, the 21-year-old Wang had believed that he was part of a broader movement. Recently, however, Wang's micro blog is silent. The reason? It's because of a woman known as "Zhao Meimei". Earlier this month, Wang joined many other users to criticize the US-based student for her wealthy overseas life, because they thought her money came from  _ since her mother was a local official. But later Wang found out that the woman student was actually being supported by her father, a hard-working businessman. "I felt guilty... Someone hid part of the truth to make a conflict. The worst thing is - I did not even have a chance to apologize to her," he says. Wang is not the only young Internet user to be confused by an online world made up entirely of broken information. According to official statistics, the number of micro bloggers in China now exceed 300 million. For private users, a micro blog can provide real-time updates from anyone a user chooses to "follow". These can range from family members to celebrities  . Information can instantly be spread through "re-tweeting". In the public area, however, a micro blog can also become a link between users and the authorities. However, with the increasing popularity of micro blogs comes a number of problems. Chen Changfeng, deputy director of the School of Journalism and Communication at Tsinghua University, stressed two major types of misbehavior that can occur on micro blogs and upset young users. "Some marketers spread fake news just to make some person or product known to more people; others use the free channel to manufacture and spread fake news and rumors like a virus," Chen says. He says that an average micro blogger receives and transmits information, but when faced with such a vast amount of information, he may lack the ability to tell the difference between the real and the fake stories. Having realized this, Internet users have come together to combat   micro blog misconduct by forming voluntary groups such as the Rumor Clarification Association. The government and individual operators of micro-blogging sites have also stepped into monitor posted content. What's the purpose of showing Wang Ganghui's experience in the passage?
To show how guilty he was. To tell us what micro blog is. To introduce the main topic of the passage. To tell us how many blog users there are in China.