题目内容：

    In the past decade, the use of social media has grown in a way that no one could have guessed. It has turned some teenagers into celebrities and turned the famous into the infamous, overnight.

A key feature of social media, however, is its volatility. Trends come and go, disappearing almost as quickly as they appeared. So, what were the key social media trends of 2018?

Short video apps such as TikTok and its Chinese equivalent(等同物) Douyin, took the world by storm. The Telegraph reported that TikTok was ranked 8th on Apple's App store in April. And Douyin had more than 300 million domestic monthly active users in June at home, CNBC said.

Why are these short videos—which are rarely longer than a few minutes—so popular? Jiang Yige, Singapore­based analyst at FengHe Fund Management, has a theory. “Short videos are just right to fill in the little gaps in our busy schedules，” he told CNBC.

These videos—apart from being very convenient—are important to teenagers because they allow them to express themselves, according to Teen Vogue.

Liza Koshy, a user of the US app Musical.ly who has over 2 million followers, said, “The sense of community that users of short video apps get is another appealing feature.”

Live streaming(直播) is a feature of our social media life that now seems as natural as sunrise. It's a pretty neat idea: You can watch anyone, anywhere, live. However, China has taken live streaming to a whole new level. In China, more than 100 million viewers monthly watch a live streaming video. Forbes thought that a number of factors had led to the popularity of live streams. Among them is viewers' ability to interact with unknown names.

However, the quick development of social media may be having side effects too. Fake news is one serious problem it causes. Materials shared on these platforms are often not checked for accuracy. The most basic content can be false and can mislead users one way or another. We use social media all the time; that doesn't mean that we understand the influence it is having on us. We should be mindful of both the time we spend on it and its impact on our minds.

1.The underlined word “volatility” in Paragraph 2 possibly means “being________”.

A.changeable B.steady

C.promising D.violent

2.According to Liza Koshy, short videos are very popular because________.

A.they are very convenient

B.they help people kill time

C.they provide a sense of community

D.they allow people to express themselves

3.What do we know about social media?

A.The information from social media is totally reliable.

B.When it comes to social media, people only know short videos.

C.People can't communicate with each other without social media.

D.There is still much room for social media to make improvement.

4.What is the author's attitude to the quick development of social media?

A.Objective. B.Subjective.

C.Favorable. D.Disapproving.