3 . Kids have 20 teeth. They fall out. New ones grow in. Adults (成人) usually have 32teeth. Teeth have a big job. They help us chew food. They help us talk. Some teeth are round. Some are sharp (尖的). We use round back teeth to grind (磨碎) food. This makes the food easy to swallow (吞咽). We use sharp front teeth to bite into food.

Teeth are helpful. What should we do to protect our teeth? Brushing keeps teeth clean. We should brush teeth in the morning and before bedtime. We should visit the dentist twice (两次) a year. Dentist clean our teeth. They check for cavities. A cavity is a part of a tooth that is not healthy (健康的). It looks like a hole. A dentist can fix that. It’s very important to take good care of our teeth.

If you look at your tongue in the mirror, you will see lots of little bumps. Taste buds are bumps on the tongue. These body parts help you taste food. Taste buds touch the food you eat. Then they send signals (信号) to your brain (大脑). Your brain makes meaning of the signals. It tells you what the food tastes like. If the food tastes bad, you know not to eat it.

Taste buds can detect (察觉) four different tastes: bitter, sour, salty and sweet. This table shows how some foods taste to most people.

Doctor:     6     Drink more water and stay in bed. If you still have a fever,come to see me tomorrow.

It is Monday morning. Jack does not go to school _______ his left foot hurts. His mother takes him _______ the doctor. The doctor checks Jack’s foot and says, “You should rest at home for two weeks. You should _______ take some medicine.” Jack is sad because he does not like _______ medicine. He cannot play football _______ his friends either. His mother says, “_______ be sad, Jack. You can watch the World Cup (世界杯) on TV.”

We have ______ senses. One of the senses is touch. We can touch things with our ______. We can also touch things with our ______. It feels hard when we touch the ______. They feel ______ when we touch the clothes. We feel cold or hot when we touch the cold or hot coffee.