Many cultures have different ideas about why people catch colds. For example in the United States, some people think that you can catch a cold if your feet get cold. So, mothers tell small children to wear warm boots in the winter. In other places, including parts of the Middle East, some people believe that strong winds cause colds. So, on trains and buses, people usually don’t like to sit next to open windows. In parts of Europe, some people think that wearing wet clothes will give you a cold. They say that after you go swimming, you should quickly put on dry clothes. Today, scientists know that colds are caused by a virus（病毒）. But the old ideas are still very strong, and many people still follow them to avoid（避免）getting ill.
What is the main idea of this reading?

A．People still believe old ideas about why they catch colds.

B．Colds are the biggest health problem in the world.

C．Some people think that strong winds cause colds.

D．You should take good care of your health in winter.

Which is NOT a cause（成因）of colds in the reading?

A．bad food

B．wet clothes

C．a virus

D．strong winds

In "people still follow them to avoid getting ill", what does "them" mean?

A．scientists

B．old ideas

C．colds

D．dry clothes

According to the reading, which of the following is NOT true?

A．There are many different ideas about how people catch colds.

B．Scientists don’t know how people catch colds.

C．Some people think that wearing wet clothes gives you a cold.

D．In the U.S., many small children wear boots in winter.

Many people in different countries have ________ ideas about why people catch colds.

A．no

B．one

C．the same

D．different