A

When you run, you put force that is equal to three times your body weight on your feet. The human foot contains twenty muscles. This means that there is a lot that can go wrong when you run.

Most sports have some kind of running or jumping. So experts at many shoe companies work hard to design good sports shoes. First, a designer enters a plan for a shoe into a computer. Engineers then improve the design. A second computer designs a model for the shoe. Then a few pairs are made. Next, the shoe is tested.

Different kinds of sports shoes are made for different uses. Some are made to help marathon runners save energy during a race. Some are made for the stop­and­go kind of running tennis players. But all sports shoes have one thing in common: they are designed to help make people's feet comfortable during sports. Today, nearly every sport has its own special shoe designed for just the kind of running that sport requires.

21£®The first in making a new shoe is to ________.

A£®make a computer

B£®design a shoe model

C£®put a design plan into a computer

D£®test several pairs

22£®Why are good sports shoes popular with people?

A£®Because they help to change body weight.

B£®Because they help to develop leg muscles.

C£®Because they are comfortable to wear.

D£®Because they are both good and cheap.

23£®Different kinds of sports shoes ________.

A£®are made in different shoe companies

B£®meet the needs of different sportsmen

C£®are of the same price

D£®are designed for people of different weight