slow down. This gives the cells more time to repair themselves.

　　The researchers say ribosomes use from 10 to 20 percent of the cell's energy to make those proteins. Price wrote that "because of this, it is impractical to destroy an entire ribosome" when it starts to break down. However, "repairing individual parts of the ribosome on a regular basis enables ribosomes to continue producing high quality proteins for longer than they would otherwise. This top quality production, in turn, keeps cells and the entire body functioning well."

Price said, "ribosome is a very complex machine, like a car." They need "maintenance to replace the parts that wear out the fastest. When tires wear out," he explained, "you don't throw the whole car away and buy a new one. It costs less to replace the old tires."

　　"Food," he said, "isn't just material to be burned---it's a signal that tells our body and cells how to respond." Price said the findings help to explain how exactly our bodies age. And this may "help us make more educated decisions about what we eat."

1.What can we know about the mice with limited calories from the study?

　A. They can keep healthy easily

　B. They need more energy to be active

　C. They can look younger than they are

　D. They will live a longer life like humans

2.What will happen to ribosomes if there are fewer calories?

　A. They will completely break down

　B. They make proteins in the cells slowly

　C. They will produce high quality proteins more

　D. They may need more time to repair themselves

3.Price explained the ribosomes' role of repairing themselves by _________.

　A. telling a story B. listing basic data

　C. making comparisons D. experimenting on mice

4.What does the text mainly deal with?

　A. Food decides how long you live

　B. Can you slow down your aging process?

　C. Eating less may help you live longer

D. Should your diet be reduced for your health?