阅读理解。

     There are two kinds of physical activity which require special training. The first demands exact careful

movements of the muscles (肌肉). This kind of activity must be strictly controlled because even a slight

movement in the wrong direction will lead a mistake. To type quickly, for example, a person needs training;

the slightest movement of a finger in the wrong direction may cause a spelling mistake. A dancer who has to

dance on the point of her shoes or turn around on one foot must be trained for a long period of time before

she can sense her own center and balance herself. You may have seen a girl walking on a rope across an

empty space, which, too, requires a lot of practice.

     The second kind of physical activity needs greater strength or extra effort. Most of us get tired if we try

to run half a mile without stopping, but a specially-trained person can do this without much effort. Three

years ago, some scientists carried out experiments, which produced meaningful and unexpected results. They

wanted to find out whether a certain amount of physical exercise would injure those suffering from heart

problems. They selected some male patients and trained them in continuous bicycle riding. They were

surprised to find that the harmful effect of given amount of physical effort was actually less on the hearts of

these trained patients than on those of the patients who were not similarly trained. This is important because

it shows that regular physical exercise enables us to make better use of the oxygen (氧气) we breathe in and

that this training, in fact, reduces the amount of work our hearts do. Many tasks which are hard for untrained

people are not hard at all for trained people.

1. The first kind of physical activity must be strictly controlled because _______.

A. a mistake in the wrong direction is dangerous to the fingers

B. a wrong movement in a direction will cause no mistakes

C. a movement in the wrong direction will cause a mistake

D. a slight movement of a finger will lead to a mistake

2. What must a dancer do before she can balance herself?

A. She must dance on the point of her shoes.

B. She must receive long-time training.

C. She must turn around on one foot.

D. She must perform again and again.

3. The experiments done by some scientists showed that ______.

A. some male patients were asked to ride bicycles regularly in the experiments

B. the physical exercise had more harmful effect on the hearts of the untrained patients

C. the physical exercise was harmless to the male patients with heart trouble

D. the physical exercise could be helpful for the patients to take in more oxygen

4. What would be the best title for this text?

A. Training Our Bodies

B. Physical Activities

C. Movement Training

D. Extra Body Effort