Your head houses the most valuable part of your body﹣your brain．As you are reading，your eyes send pictures to your brain which makes meaning from what you see．Your brain helps you to remember and think，and makes sure your body is doing what it should． What is my skin（皮肤） for？
Your skin covers your body．In most parts of your body，the skin is just as thick as half a centimeter．If you have your skin cut，it will have a quick cure and stop viruses from getting into your body．Your skin also helps you feel the heat and coldness of the environment around you．Hair grows from inside the skin．
When you feel hot，extra heat comes out through your skin．As a result，your body temperature drops． How do I move？
Muscles（肌肉） are found in most parts of your body．They work with your bones to help you move﹣whenever you cry or smile，eat or speak，walk or dance，etc．
Why do I breathe？
Your body needs to take in oxygen from the air and give out the unwanted carbon dioxide in the body．
When you breathe，air comes through your nose and mouth into your lungs（肺） where oxygen flows to different parts of your body．
What makes me sneeze？
When dust or a strong smell gets into your nose，you sneeze．This is the way your body cleans up the dust in your nose．Your lungs push out the air and try to clear your nose．
What does my heart do？
Your heart is a very special muscle．It is slightly bigger than your fist （拳头） and grows bigger as you do．If you place your hand on your heart，you will feel your heart beating which forces blood to move around your body．
39．The underlined word“houses”in the passage probably means ． A．locks B．stores C．creates D．builds 40．What is the true fact about your body？ A．Our heart is the same size from birth． B．We take in carbon dioxide to stay alive．
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C．Our muscles stop working when we nod． D．Sneezing is a way to clear our nose．
41．If you have no skin covering your body，what would happen？ A．Extra heat can only stay inside our body． B．Viruses can’t get into our body easily． C．We can’t feel the changes in temperature． D．Our body can be guarded by our hair． 42．Which is the best title for this passage？
A．How Your Body Works. B．What Your Body Needs. C．Why Your Body Grows. D．When Your Body Moves．
C
In northern China during spring, big sandstorm often make trouble for people. Sandstorms usually happen in spring. They have happened in more than 10 provinces in northern China this year. People in southern China don’t have to worry about this kind of bad weather. Most of the sand comes from the north of China. In northern China, lots of places have few trees and don’t get much rain. When there aren’t many trees, the ground can’t keep enough water. Over the years, the ground dries up and turns to sand. When spring comes and the ice melts, the ground becomes loose. Strong winds take the loose sand into the sky. Besides, in northeast China, there lies some vast deserts.
Sandstorms are bad for people’s health. If people breathe in too much sand, they will cough or have serious illnesses. Sandstorms also give farmers lots of problems. Sometimes their sheep get lost in the storms and never come back home. The winds also tear the farmers’ houses down.
What can you do to stop sandstorms? Here’s a piece of advice. Ask your parents to help you plant some trees this spring. If you see people cutting down too many trees, tell them about the dangers of sandstorms, and ask your government to stop them. 43. When do sandstorms usually happen?
A. In summer. B．In spring. C．In winter. D．In autumn
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