题目内容：

Although considered an excellent exercise, jumping rope has never received widespread acceptance because of two reasons. First, most people recognize jumping rope as an excellent form of cardiovascular(心血管的)exercise, but they also believe that it is simply too difficult. In other words, they don’t think they’ll be able to continue jumping for the near 20 minutes in order to achieve a beneficial physical effect. Second, many regard it as somewhat boring and overly repetitive(重复乏味的)—not as something fun or enjoyable.

As a matter of fact, jumping rope can be great fun as long as you find a proper way to practise it. Instead of doing the usual two-foot bounce(跳)over and over again, players good at rope-jumping often change their pattern every 10 or 20 jumps: a single bounce, a double-bounce, a skip, a knee-up, side swings, as well as a variety of other easy-to-learn free-style rope-jumping.

Nowadays researchers are discovering that jumping rope also prepares the brain for learning. It is an exercise allowing both brain hemispheres(半球)to perform equally to each other.

In short, jumping rope can be a life-long activity requiring little equipment, time and space, yet leading to a much healthier life.

1. One reason that can explain why rope-jumping has not spread widely is that

　　　.

A. it benefits the cardiovascular system

B. it is too difficult for people to learn to jump

C. it is believed to be boring and repetitive

D. it requires little equipment, time and space

2. The first sentence in Paragraph 2 means that　　　in rope-jumping.

A. there is only one proper way to follow

B. the usual way should not be used again

C. the easiest way is always the best one

D. there are different kinds of ways to follow

3.According to the researchers, jumping rope　　　.

A. only prepares the brain for learning

B. is suitable for students only

C. helps both brain hemispheres work together

D. can be dangerous for old people

4.What does the writer think of rope-jumping?

A. He is strongly against it.

B. He is for it.

C. The passage doesn’t mention it.

D. He knows little about it.