阅读理解。

You are watching a film in which two men are having a fight. They hit one another hard. At the start they
only fight with their fists. But soon they begin hitting one another over the heads with chairs. And so it goes on
until one of the men crashes through a window and falls thirty feet to the ground below. He is dead!Of course
he isn't really dead. With any luck he isn't even hurt. Why? Because the men who fall out of high windows or
jump from fast moving trains are professionals. They do this for a living. These men are called stuntmen. That
is to say, they perform tricks. There are two sides to their work. They actually do most of the things you see
on the screen. For example, they fall from a high building. However, they do not fall on to hard ground but on
to empty cardboard boxes covered with a mattress (床垫). Again, when they hit one another with chairs, the
chairs are made of soft wood and when they crash through windows, the glass is made of sugar! But although
their work depends on trick of this sort, it also requires a high degree of skill and training. Often a stuntman's
success depends on careful timing. For example, when he is 'blown up' in a battle scene, he has to jump out
of the way of the explosion just at the right moment.
Naturally stuntmen are well paid for their work, but they lead erous lives. They often get seriously
injured, and sometimes killed. A Norwegian stuntman, for example, skied over the edge of a cliff (悬崖) a
thousand feet high. His parachute (降落伞) failed to open, and he was killed. In spite of all the risks, this is no
longer a profession for men only. Men no longer dress up as women when actresses have to perform some
erous action. For nowadays there are stuntgirls tool.

1. Stuntmen are those who ______.
[ ]
A. often dress up as actors
B. prefer to lead erous lives
C. often perform seemingly erous actions
D. often fight each other for their lives
2. Stuntmen earn their living by ______.
[ ]
A. playing their dirty tricks
B. selling their special skills
C. jumping out of high windows
D. jumping from fast moving trains
3. When a stuntman falls from a high building, ______.
[ ]
A. he needs little protection
B. he will be covered with a mattress
C. his life is unprotected
D. his safety is generally all right
4. Which of the following is the main factor (因素) of a successful performance?
[ ]
A. Strength.
B. Exactness.
C. Speed.
D. Carefulness.
5. What can be inferred from the author' s example of the Norwegian stuntman?
[ ]
A. Sometimes an accident can occur to a stuntman.
B. The percentage of serious accidents is high.
C. Parachutes must be of good quality.
D. The cliff is too high.