【推荐1】As we all know, trees are important to our life. They provide us with food, wood and most importantly, oxygen. Now there is one more thing we can add to this list—blocking out harmful bacteria in water.

The discovery was made by some scientists and high school students who were seeking for a natural water filter(过滤器)—one that could help people in developing countries that don’t have access to modern water systems.

The researchers, led by Rohit Karnik, a professor ,decided to turn to trees for help because they were able to allow liquid to flow through while blocking out air bubbles(气泡）.

They began by cutting 1.5-inch-wide sections of tree bark from the branch of a white pine tree. The researchers then tested the wood’s filtering ability by pouring water containing red dye particles(染料颗粒)of different sizes through. To their surprise, they found it was effective in trapping all the particles. Encouraged, the team did another experiment, this time with water containing bacteria. Sure enough, the bark held back 99%of the bacteria, allowing only 1% to flow through.

Mr. Karnik said the bark was able to filter water containing much smaller particles. This means that it can be used to get rid of most of the bacteria. However, what troubles them is that tree bark cannot hold back viruses, which tend to be much smaller.

Though the experiment is successful, we must remember one thing—the bark only works when damp. This means that before this natural filter can be put to practical use, the researchers will have to figure out how to keep the bark damp, or find a way to keep the bark’s great filtering ability even when it’s dry.

But the study is not done. The researchers plan on testing other types of trees, including those flowering trees. They think those may be more effective in trapping smaller particles and even viruses.

1. How will the discovery affect the world?

A．No harmful bacteria will be found in water.

B．There will be no water pollution around the world.

C．More pine trees will be planted around the world.

D．Clean water will be more accessible in developing countries.

2. What problem troubles the researchers when using the trees bark as a water filter?

A．Viruses cannot be prevented.

B．Tree bark should be wet.

C．It’s hard to remove air bubbles.

D．Not all bacteria can be held back.

3. Why does the team plan to do other experiments?

A．To find other natural water filters.

B．To improve the filtering ability of other trees.

C．To find a way to keep the bark wet.

D．To test the filtering ability of other trees.

4. In which column of a newspaper can we read this text?

A．Culture.	B．Science.
C．Lifestyle.	D．Society.

【推荐2】Danelien van Aalst at the University of Groningen and her co-workers have done research on how relative age (相对年龄) affects popularity among 14 to 15-year-olds.

Researchers surveyed more than 13,000 teenagers in England, Sweden and the Netherlands on who they thought was the most popular in their class. Then the researchers gave each student in their classroom a popularity score linked to their birth month as well as their age position in their class. They discovered this: the older the student was, the more likely he or she was to be considered popular.

“A child enters school before or after a certain cut-off date and that determines how old or young you are relative to your year group,” says van Aalst. “We found that if you’re born right after the cut-off date, which makes you one of the oldest members of your class, you’re going to be popular.”

They found that the same effect also applied at the year-group level. Here, it was the children who were the oldest relative to all of their peers in the year group-rather than just those in their own class-that were the most popular.

All three countries showed roughly the same pattern (模式). However, at the classroom level, it was in the Netherlands that the pattern was the strongest. This is partly because the country has a system of grade retention - when students don’t meet their academic requirements, their teachers will hold them back a year, which means they then become the oldest in their class and often the most popular.

This relative age effect has also been shown in other areas. “Relative age has earlier been proved to affect school performance-relatively older children do better in school,” says Herman van de Werfhorst at the University of Amsterdam. Similarly, previous research has shown that older children tend to be better at sports than younger students in the same year group.

1. How did the researchers know who the popular students were?

A．By recording students’ performance.	B．By studying earlier research results.
C．By collecting answers from students.	D．By comparing the ages of students.

2. What does the underlined word “that” refer to in paragraph 3?

A．Popularity.

B．Relative age.

C．The survey data.

D．The cut-off date.

3. What might happen to students held back a year in Netherlands?

A．Their teachers would be happy to have them in the class.

B．It would be difficult for them to pass the exams in Netherlands.

C．They might gain more popularity than others in the same year group.

D．They might be the most popular among the peers of the three countries.

4. What does the passage mainly tell us?

A．The older a child gets, the wiser he or she will be.

B．Many students want to be held back to be popular.

C．Older children are likely to perform better in school.

D．Older children are often more popular than their younger peers.