Lichens (地衣) are difficult to see. They don’t move. They often mix into the living place. You might not even recognize one if you are looking right at it.

Lichens live on rocks, branches, houses, and even metal street signs. You can find these colorful organisms (微生物) almost everywhere — from deserts to rainforests, and from Antarctica to Africa. They’ve traveled in outer space, and some scientists think there might even be lichens on Mars.

What you probably don’t realize is that a lichen is more than a single thing. It includes two different types of living organisms: a fungus (菌类) and an alga (藻类). Neither of these organisms is a plant, so the lichen isn’t a plant either.

Through photosynthesis (光合作用), the alga gets the sun’s energy to make food for the fungus, which is the place for the alga to live in. However, the alga cannot leave the fungus.

Around the world, scientists have found tens of thousands of types of lichens. Many may not even have been discovered yet. As scientists continue to find new kinds of lichens, they are also working to understand how they are connected to one another. By putting together a lichen family tree, they hope to understand why so many different types of lichens have grown in so many places around the world.

Many researchers are trying to understand basic facts about the organisms and their connections. Researchers are also using lichens to examine the health of the environment.

What do we know about lichens according to the passage?

A. They will die if they leave Earth.

B. There are more lichens than plants on Earth.

C. They look similar to the environment around them.

D. They are too small to be easily seen by people.

What does the second paragraph mainly talk about?

A. The way lichens live.

B. The natural environment of lichens.

C. The way lichens work as organisms.

D. The family tree of lichens.

Which of the following statements is NOT the scientists’ purposes of studying lichens?

A. To understand basic facts about them.

B. To creat a lichen family tree.

C. To understand how lichens are related to each other.

D. To understand why lichens can live in different places.

We can know from the passage that __________.

A. lichens can be used to better understand the environment

B. lichens don’t have any differences in colors or sizes

C. lichens don’t use photosynthesis like a green plant

D. scientists have discovered every kind of lichen

A  rainfores（雨林）is an area covered by tall trees with the total high rainfall spreading quite equally through the year and the temperature rarely dipping below 16℃.Rainforests have a great effect on the world environment because they can take in（吸收） heat from the sun and adjust （调节）the climate. Without the forest cover, these areas would reflect more heat into the atmosphere，warming the rest of the world .Losing the rainforests may also influence wind and rainfall patterns, potentially causing certain natural disasters（灾害） all over the world.

In the past hundred years, humans have begun destroying rainforests in search of three major resources (资源): land for crops, wood for paper and other products, land for raising farm animals. This action affects the environment as a whole. For example，a lot of carbon dioxide(二氧化碳)in the air comes from burning the rainforests. People obviously have a need for the resources we gain from cutting trees but we will suffer much more than we will benefit（受益）.

There are two main reasons for this. Firstly, when people cut down trees, generally they can only use the land for a year or two. Secondly, cutting large sections of rainforests may provide a good supply of wood right now, but in the long run （长远看）it actually reduces the world’ s wood supply.

Rainforests are often called the world’s drug store. More than 25% of the medicines we use today come from plants in rainforests. However, fewer than 1% of rainforest plants have been examined for their medical value. It is extremely likely that our best chance to cure diseases lies somewhere in （在于）the world’s shrinking rainforests.

1..．Rainforests can help to adjust the climate because they________.

2..．What does the word “this” underlined in the third paragraph refer to?

3..What might be the best title for the text?

There are many international organizations which work to save and protect endangered species and natural environment. If you would like more information about any of the organizations listed blow, you can write to the addresses given.

Since people first sent rockets into space in the 1950s, we have been leaving behind all sorts of things. Some of them, like the camera, were lost by astronauts while they did work outside their spaceship. But much of the space junk is made up of little pieces of things that were once bigger objects, until they struck each other and broke apart.

Some things we send into space fall back toward the earth and burn up in the atmosphere. But larger pieces sometimes survive the extreme heat and hit the ground or the ocean at great speeds. So there is always concern that something may fall from the sky and do some harm.

But space junk falling on housetops (屋顶) is not the biggest worry. Scientists are concerned about what happens when an empty rocket strikes another while orbiting (绕轨道飞行) the earth. Two big things become many smaller things. They then hit other things. The pieces get smaller and smaller until they form a cloud of junk that blocks the path of future space vehicles.

So what can be done to clean up the space around our planet? Marco Castronuovo, an Italian researcher, talks about sending a satellite into space that would get very close to some of the larger pieces of space junk. The satellite would connect a small rocket to the useless object. When the rocket explodes, it pushes the junk into a lower and slower orbit, nearer the earth. After a time, the junk burns up in the atmosphere.

Mr. Castronuovo has proposed (提议) using a number of small satellites with robotic arms. One arm would catch the space junk, and another arm would connect the rocket. He imagines that each satellite would jump from one large piece of junk to another. He thinks this method could destroy about ten large objects each year.

Scientists have been concerned about space junk for many years. Right now, the costs of the clean-up have been too great. Mr. Castronuovo says his system could be put in place for a much more reasonable amount of money.

1.Much of the space junk _____.

A．was thrown by the astronauts

B．is from broken spaceship

C．is made up of small pieces of things

D．returns to the earth piece by piece

2.Scientists are most worried that the space junk _____.

A．will stop the future space vehicles

B．will do harm to the atmosphere

C．will fall on the housetops

D．will burn up in space

3.What does Marco Castronuovo think of his system?

A．It can remove space junk completely.

B．It can save a large amount of money.

C．It can create a large amount of space.

D．It can develop robotic technology.

Organic foods are produced according to certain production standards, meaning they are grown without the use of conventional pesticides, or chemical fertilizers and that they were processed without food additives. Livestock are raised without the routine use of antibiotics（抗生素）or growth hormones. In most countries, organic produce must not be genetically modified. They may also be required to be produced using energy-saving technologies and packaged using recyclable materials when possible.
Early consumers interested in organic food would look for non-chemically treated, fresh or minimally processed food.
They mostly had to buy directly from growers: “Know your farmer, know your food” was the motto. Personal definitions of what constituted ( 组成)“organic” were developed through first-hand experience: by talking to farmers, seeing farm conditions, and farming activities. Historically, organic farms were relatively small family-run farms — which is why organic food was once only available in small stores or farmers’ markets.
However, since the early 1990s organic food has had growth rates of around 20% a year. As of April 2008, organic food accounts for 1 - 2% of food sales worldwide. Currently organic food production is legally regulated. Many countries require producers to obtain organic certification in order to market food as organic.
Several studies have attempted to examine and compare conventional and organic systems of farming. The general consensus（共同看法）is that, in the short term, organic farming is less damaging for the following reasons:
● Organic farms do not release synthetic pesticides (合成农药) into the environment — some of which have the potential to harm soil, water and local wildlife.
● Organic farms are better than conventional farms at keeping diverse ecosystems, i.e., populations of plants and insects, as well as animals.        
● Organic farms are more energy efficient and produce less waste.
Another report published in March 2008 by The Organic Center claims that organic food is on average 25% more nutritious than conventional food.     
However, many critics believe that the increased land needed to farm organic food could potentially destroy the rainforests and wipe out many ecosystems. And organic products cost 10 to 40% more than similar conventionally produced products. Processed organic foods in supermarkets are 65% more expensive.
1. Early consumers knew what food was “organic” by _______.
A. firsthand experience                                     B. the “certified organic” label tag
C. its packaging                                                      D. examining its organic certification
2. We can infer that _______.
A. in America, organic food can only be bought in small stores or farmers’ markets
B. organic food is also available in large supermarkets at present
C. organic food is produced by large-scale farms
D. organic food is often beautifully packaged
3. According to the passage, organic food is considered as _______.     
A. junk food              B. delicious snacks               C. green food      D. conventional food
4. What is the main idea of the last paragraph?
A. The benefits of organic food.                               B. The cost of organic food.
C. The disadvantages of organic food.                   D. Organic food and conventional food.
5. Which of the following statements does NOT support the view that organic farming is more environment-friendly?
A. Organic food is generally thought to be more nutritious.
B. Organic farms are more energy efficient and produce less waste.
C. Organic farms are better than conventional farms at maintaining varieties of plants, insects and animals.
D. Organic farms do not release synthetic pesticides into the environment.