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Human Teeth
人的牙齒
Teeth are the hardest thing in the human body.
牙齒是人體中最堅固的東西。
They are not made of bone.
它們不是由骨骼構成的。
They are made of enamel, gum and so on.
而是由牙釉質，牙齦等構成的。
People use teeth when they eat something or tear something.
人們用牙齒吃東西或撕東西。
How many teeth do people have?
人有多少顆牙呢？
When they are young, they have 20 teeth.
小時候，人有20顆牙。
And when they get older, they have 32 teeth all together.
長大后，人總共有32顆牙。
