When did you last see a polar bear(北极熊）? On a trip to a zoo,perhaps?  If you had attended a winter activity in New York a few years ago,  you would have seen a whole polar bear club.  These "Polar Bears" are people who meet frequently in the winter to swim in freezing cold water.  That day, the air temperature was 3℃, and the water temperature was a little higher.  The members of the Polar Bear Club at Coney Island, New York are usually about the age of 60.  Members must satisfy two requirements.  First, they must get along well with everyone else in the group; this is very important because there are so many different kinds of people in the club.  Polar Bears must also agree to swim outdoors at least twice a month from November through February.
Doctors don't agree about the medical effects of cold-winter swimming.  Some are worried about the dangers of a condition in which the body's temperature drops so low that finally the heart stops.  Other doctors, however, point out that there is more danger of a heart attack during summer swimming because the difference between the air temperature and water temperature is much greater in summer than in winter.
The Polar Bears themselves are satisfied with the benefits of cold-water swimming.  They say that their favorite form of exercise is very good for the circulatory system(循环系统）because it forces the blood to move fast to keep the body warm.  Cold-water swimmers usually turn bright red after a few minutes in the water.  A person who turns blue probably has a very poor circulatory system and should not try cold-water swimming.
　　The main benefits of cold-water swimming are probably mental.The Polar Bears love to swim all year round;  they find it fun and relaxing.  As one 70-year-old woman says,"When I go into water, I pour my troubles into the ocean and let them float away."
The members of the Polar Bear Club must meet the following requirements except that_____.

A．they must swim outdoors at least 8 times in the four cold months

B．they must reach the age of 60

C．they should be easy to make friends with

D．they must agree to swim outdoors from November through February

According to the passage, some doctors believe it is true that_____.

A．Polar Bears are bears swimming in freezing water

B．cold-water swimming can make the body temperature dangerously high

C．you are healthy if cold-water swimming turns your skin color blue

D．cold-water swimming causes more heart attacks in summer than in winter

The Polar Bears like to swim year-round, for_____.

A．it is an easy way to keep the body warm in winter	B．they can remain young
C．they find it enjoyable and interesting	D．they might meet fewer troubles in life

The passage is mainly about_____.

A．the requirements of the Polar Bear Club

B．a group of cold-water-swimming livers

C．the Polar Bears' life in New York

D．doctors' ideas about cold-water swimming