Let’s try doing the following experiment.

What to do:

Use string to hang a paper clip or other small object at about chest(胸部)level.

Pick up a stick,such as a broom handle. Take three or four steps away from the paper clip.

Now close one eye and walk toward the paper clip. Try to touch it with the tip of the stick. If you miss,try again,still keeping one eye closed. Now try it with both eyes open and see if it’s easier to do.

How it works:

In the experiment,you have to judge how far away the paper clip is. Your brain has several ways of doing this.

One simple way depends on how much your eye has to focus(聚焦)itself. Using only one eye,most people will find it difficult to touch the paper clip on the first try,but the brain still gets some information about distance—though not much.

Your brain can judge distance much better when you look at something with both eyes. In fact,your brain has more than one way to use both eyes in judging distance. For example,to see anything clearly,you have to make both of your eyes point at the object. When you look at a nearby object,your eyes turn inward. You can feel this happening if you look at the tip of your finger and move your finger toward your nose.

Your brain gets information from the eyes about how much they are pointing toward each other. Using that information,the brain can tell how far away any object is,whether it is a basketball or a paper clip.

1.How many materials do we need at least to do the experiment?

A.Two B.Three C.Four D.Five

2.The passage is mainly about that with eyes our brain can judge .

A.how big an object is

B.how high an object is

C.how far away an object is

D.how much information an object is

3.Which of the following is true according to the passage?

A.Our brain judges distance in one way when we use both eyes.

B.Our brain cannot judge the distance of a small object but a big one.

C.How much our eyes focus helps our brain judge the size of an object.

D.How much our eyes focus helps our brain judge the distance of an object.

4.From the experiment we can infer(推断) .

A.with one eye we can see an object as clearly as we use two eyes

B.our eyes turn towards the inside when we look at an object very near

C.within 3 or 4 steps,the nearer an object is,the more clearly we can see it

D.our brain can hardly get any information about distance when we use one eye

There is little rain in desert. Because deserts are so dry, they have no “quilt” to help stop the soil from going away. As a result, they may get very hot during the day with the sun shining, but don’t hold the heat overnight. Many deserts can quickly get cold once the sun goes down. Some deserts can reach temperatures of over 100 degrees F during the day and then drop below freezing (32 degrees F) during the night.

The largest hot and dry desert in the world is the Sahara Desert in Northern Africa. The Sahara is a sandy desert with great sand hills. It covers over 3 million square miles of Africa. Other large deserts include the Arabian Desert in the Middle East, the Gobi Desert in Northern China and Mongolia, and Kalahari Desert in Africa.

Animals that live in the desert are also used to needing little water. Many get all the water they need from the food they eat. Other animals keep water that they can use later. The camel stores up fat in its hump while other animals keep something they need in their tails.

Only certain types of plants can live in the terrible environment of the desert. You won’t see a lot of tall trees in the desert. Most plants have a way to keep water in their leaves, or trunks so they can live a long time without water.

Now deserts cover around 20% of the world’s land, but they are growing. This is called desertification and is caused by different reasons including human activities. The Sahara Desert is growing larger and larger each year. What should we do with it ?

1.How is the weather during the night in the desert?

A. Hot. B. Cold. C. Cool.

2.Where does the camel store up fat?

A. In its hump. B. In its stomach. C. In its tail

3.Why won't we see a lot of tall trees in the desert?

A. Because of few people there.

B. Because of the sun shining.

C. Because of the terrible environment

4.How much of the land do deserts cover in the world?

A. One fifth. B. Less than 10%. C. Two fifths

5.Is the Sahara Desert growing or not?

A. Nobody knows it.

B. It's growing.

C. It's not growing.

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