D．the lower the class is, the faster the rafting is

　　　22．If 10 college students are to participate in the Dam Release White & shy; water Rafting, how much money will be paid in total?

　　　A．$610. B．$330.

　　　C．$390. D．$310.

　　　23．Family Style White-water Rafting is unique in that ____.

　　　A．it allows people to swim in the river B．the river water is very clean

　　　C．it provides a barbeque lunch for free D．it offers a free bird­watching activity

　　B

　　Recently some American scientists have given a useful sincere piece of advice to people in industrialized nations that they would be much healthier if they ate more of the same kind of food eaten by humans living more than 10,000 years ago.

　　The scientists say that the human body has changed very little since humans first appeared on the earth, but the way we live has changed greatly. Our body has not been able to deal with (处理,对付)these changes in life style and this has led to new kinds of sicknesses. These new sicknesses were not known in ancient times, so they are called " diseases of civilization". Many cancers and diseases of the blood system, including heart attacks and strokes (中风) are examples of such diseases.

　　Scientists noted that people in both the Old Stone Age and the New Stone Age enjoyed very little alcohol (酒精) or tobacco (烟草), probably none. Ancient people also got a great deal of physical exercise, but a change in food is one of the main differences between life in ancient times and that of today.

　　Stone-age people hunted wild animals for their meat, which had much less fat than domestic or tame ones (家畜). They also ate a lot of fresh wild vegetables and fruits. They didn't have milk or any other dairy products, and they made very little use of grains. But today, we eat a large amount of these. We eat six times more salt than our remote ancestors (祖先). We eat more sugar. We eat twice as much fat but only one third as much protein (蛋白质) and much less vitamin C.

People today probably do not want to live the way people thousands of years ago did, but scientists say that we would be much healthier if we ate much the same way as remote ancestors