13．By now，we are all aware that social media has had a tremendous influence on our culture，in business，on the world-at-large．Social media websites revolutionized the way people communicate and socialize on the Web．However，aside from seeing your friends'new baby on Facebook，or reading about Justin Bieber's latest conflict with the law on Twitter，what are some of the real influences？
Social networks offer the opportunity for people to re-connect with their old friends and
acquaintances，make new friends，share ideas and pictures，and many other activities．Users can keep pace with the latest global and local developments，and participate in campaigns and activities of their choice．Professionals use social media sites like LinkedIn to enhance their career and business development．Students can work together with their peers to improve their academic and communication skills．
Unfortunately，there are a few downsides too to social networking．If you are not careful，
immoral people can target you for cyber bullying and disturbance on social sites．School children，young girls，and women can fall victim to online attacks which can create tension and suffering．If you are a victim of cyber bullying，do not take it lying down，but try to take appropriate legal action against the attacker．
Many companies have blocked social networks as addicted employees can distract themselves
on such sites，instead of focusing on work．In fact，studies show that British companies have lost billions of dollars per year in productivity because of social media addiction among employees．
Also，what you carelessly post on the Net can come back to trouble you．Revealing（ 泄露）
personal information on social sites can make users vulnerable（易受伤害的）to crimes like identity theft，stalking，etc．Many companies perform a background check on the Web before hiring an employee．If a potential employee has posted something embarrassing on social media，it can greatly affect their chances of getting the job．The same holds true for our relationships too，as our loved ones and friends may get to know if we post something undesirable on social networks．
Social media has its advantages and drawbacks as each coin has two sides．It is up to each user to use social sites wisely to enhance their professional and social life，and exercise caution to ensure they do not fall victim to online dangers．
67．Paragraph 2mainly shows that social networksA．
A．benefit users in various ways
B．offer offer professionals good chances
C．guide users to make right choices users to make right choices
D．help students finish their homework
68．Faced with problems caused by social media，some companiesD．
A．take legal action against the attackers
B．avoid posting embarrassing information
C．refuse to hire potential addicted employees
D．forbid the use of social networks during work time
69．The main purpose of this passage is toD．
A．share experiences in using social media
B．provide some advice on social problems
C．raise public awareness of social problems
D．remind people to wisely use social media
70．Which of the following shows the development of ideas in this passage？B
I：Introduction P：Point Sp：Sub-point（次要点） C：Conclusion．
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