1 . Unsolved Mysteries About the Planet Earth

◆Mystery 1: Where did all the water come from?

Water covers 70 percent of Earth’s surface and earns it the nickname “the blue planet”. And where did it come from? The most popular scientific theory states that the water came from several violent asteroids (小行星) filled with ice. Another suggests that the water actually has been around since Earth’s formation. However it happened, though, it’s certainly worked out well for Earth’s life forms.

◆Mystery 2 :What about all the oxygen?

Another thing is the planet’s oxygen. Tiny creatures released oxygen as a waste product, filling the atmosphere with it. After that, the level of oxygen in Earth’s atmosphere went wildly up and down until it finally calmed down around 540 million years ago. Since then, it’s remained at about the breathable level we experience today. But what caused it to be suddenly steady?

◆Mystery 3: What caused the Cambrian (寒武纪) Explosion?

The Cambrian Explosion refers to the explosion of complex life forms that occurred on Earth about 540 million years ago. Before then, life had consisted mostly of bacteria. But at the beginning of the Cambrian period, complex creatures began developing at a rate never seen before. Suddenly, life forms had brains, eyes, and bones. Most living creatures today can trace their blood back to the Cambrian period.

◆Mystery 4: Will we ever be able to predict earthquakes?

We still haven’t been able to come up with a way to accurately predict earthquakes. We can certainly try, but our current technology cannot predict them exactly. We know that earthquakes start when rocks crack underground and send earthquake waves toward the surface, but we haven’t figured out why that happens, or how to predict it.

1. Which of the following is true according to the text?

A．Earth is called the blue star because of water coverage.

B．The level of oxygen has been steady all the time.

C．Complex creatures had rapid development after the Cambrian period.

D．We know nothing about predicting earthquakes.

2. Which of the following is true about Mystery 4?

A．It is the oldest mystery of the four.

B．It will be solved in the near future.

C．It is the most difficult mystery to solve.

D．It is a matter that is of practical significance.

3. Where is this text most likely from?

A．A diary.	B．A geography book.
C．A novel.	D．A magazine.

2 . A new report from the U. K. says more than 1 in 5 teens there spend five hours or more per day on social media. And the heavier users of social media get to bed later and get poorer quality sleep. The new study was based on self-reported survey data from nearly 12,000 teenage participants in the U. K. Millennium Cohort Study.

Megan Moreno, a researcher at the University of Wisconsin Madison, says social media is too often described as either entirely good or bad, when the reality is more complicated(复杂的) for teens. Social media may have its problems, but it is the way that they stay in touch with each other,” she says.

Perhaps unsurprisingly, the study found a link between high social media usage and poor sleep patterns. Especially, teens who are heavier users of social media go to sleep later. And the researchers note late bedtime is linked with poorer academic and mental health consequences.

Holly Scott, a researcher at the University of Glasgow, isn’t sounding the alarm. She says, “It’s easy to look at the results of this and think, ‘We should just get teenagers to spend less time on social media. ‘ I think that’s an understandable response, but what I really encourage people to do is look beyond that. “ She says people should pay attention to the important emotional ,cognitive (认知的)and social factors when teenagers are using social media.

Scott stresses that the study is pointing to a connection between social media and poor sleep, but not necessarily explaining cause and effect.

“Certainly some teens do say they struggle to get away from social media at night - they might be worried about missing out on things, or affecting their friends by not answering messages -and they stay up late for that,” she says. “As for some of those young people, they have a naturally later body clock and they are passing their free time at night on social media until they^’e ready to fall asleep.”

1. What’s the purpose of the new study in the U. K. ?

A．To find the benefits of using social media.

B．To know the effects of using social media.

C．To promote the development of social media.

D．To prove the growing popularity of social media.

2. What’s Megan Moreno’s attitude towards social media?

A．Positive.

B．Doubtful.

C．Objective.

D．Confused.

3. What does Holly Scott encourage people to do?

A．Make better use of social media.

B．Spend less time on social media.

C．Study how social media influences teens.

D．Understand why teens like using social media.

4. In which section of a newspaper does this passage most probably appear?

A．Health.

B．Education.

C．Science.

D．Entertainment.