take up today. You don't need any special equipment except a good pair of shoes; and you don't have to worry about resources and your purse. Simple and free, power walking can also keep you fit. If you walk regularly, it will be good for your heart and bones. Experts say that 20 minutes of power walking daily can make you feel less anxious, sleep well and have better weight control.

　　Whatever sport you take up, you can make it greener by using environment­friendly equipment and buying products made from recycled materials. But the final goal should be "green gyms". They are better replacements for traditional health clubs and modern sports centers. Members of green gyms play sports outdoors, in the countryside or other open spaces. There is no special requirement for you to start your membership. And best of all, it's free.

　　8．Which of the following is the author most probably in favor of?

　　A．Cycling around a lake.

　　B．Motor racing in the desert.

　　C．Playing basketball in a gym.

　　D．Swimming in a sports center.

　　9．What do we know about golf from the passage?

　　A．It is popular in Portugal and Spain.

　　B．It causes water shortages around the world.

　　C．It pollutes the earth with chemicals and wastes.

　　D．It needs water and electricity to keep its courses green.

　　10．The author uses power walking as an example mainly because________.

　　A．it is an outdoor sport

　　B．it improves our health

　　C．it uses fewer resources

　　D．it is recommended by experts

　　11．The author writes the passage to________.

　　A．show us the function of major sports

　　B．encourage us to go in for green sports

　　C．discuss the major influence of popular sports

　　D．introduce different types of environment­friendly sports

　　D

　　Two recent studies have found that punishment is not the best way to influence behavior.

　　One showed that adults are much more cooperative if they work in a system based on rewards. Researchers at Harvard University in the United States and the Stockholm School of Economics in Sweden did the study.

　　They had about two hundred college students play a version of the game known as the Prisoner's Dilemma. The game is based on the tension between the interests of an individual and a group. The students played in groups of four. Each player could win points for the group, so they would all gain equally. But each player could also reward or punish each of the other three players.

　　Harvard researcher David Rand says the most successful behavior proved to be cooperation. The groups that rewarded it the most earned about twice as much in the game as the groups that rewarded it the least. And the more a group punished itself, the lower its earnings. The study appeared last month in the journal Science.

　　The other study involved children. It was presented last month in California at a conference on violence and abuse. Researchers used intelligence tests given to two groups. More than eight hundred children were aged two to four the first time they were tested. More than seven hundred children were aged five to nine. The two groups were retested four years later, and the study compared the results with the first test. Both groups contained children whose parents used physical punishment and children whose parents did not.

　　The study says the IQs of the younger children who were not spanked were five points higher than those who were. In the older group, the difference was almost three points. The more they are spanked, the slower their mental development.

　　12．According to the first study, we mainly infer that ________.

　　A．the game is called Prisoner's Dilemma

B．the less a group punished itself, the lower its earnings