20．When we have small cuts in the skin（皮肤），something strange may happen．The cuts are able to heal（痊愈） themselves in a few days．How does this happen？Read on，and you will find out the secret．
Every living thing on the earth is made up of cells（细胞）．Cells grow and make new cells．Most cells are very small and we can't see them with our eyes．Different cells have different uses．Our skin cells are special ones．The cells on the outside of our skin are old dead cells．New skin cells are right under the outside．These are the living skin cells．They work for our bodies．They help protect our bodies and heal cuts．
Our bodies make skin cells all the time．As the old cells fall off，new cells grow in the same place．Each person makes about 18kg of skin cells during his or her life．Outside skin cells fit together closely with no gaps（缝隙） between them．When you cut yourself，you can harm your skin cells．A small cut will not be harmful．Your skin will quickly heal itself by making new skin cells．How do skin cells work？First，the cells near the cut get bigger and move into the gap．Next，these bigger cells meet in the middle．They form a new layer（层） of skin cells．Finally，new cells will grow until the gap disappears．In this way，your skin can grow and get well itself．How amazing the small cells are!Next time you have a cut，don't worry about it．Maybe in a few days，you will be surprised to find it healed．
35．From the passage，we know that cellsD．
A．are large and we can see them with our eyes
B．can heal few cuts themselves
C．are in everything on the earth
D．can grow and make new cells
36．Skin cells heal cuts in three steps．Bis the right order．
37．Which of the following is TRUE according to the passage？B
A．Each person can make 18kg of skin cells every day．
B．Different cells have different uses in our bodies．
C．The skin cells have little work to do in the body．
D．Every living thing on the earth is made up of skin cells
38．The best title for this passage should beA．
A．How Skin Cells Heal Cuts
B．The Importance of Skin
C．How to Protect Our Fingers
D．The Importance of Cells．
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