【2015河北】阅读短文，并按要求完成71~75题。
Many people believe that yellowing and wetness are the greatest enemy of stamps. In fact, stamps are afraid of not only wetness, but also light and dirty things. People protect their stamps in several different ways.
To protect stamps, we should never touch the stamps with our hands. This avoids moving dirty things onto them. Stamp tweezers (镊子) should be used in all conditions.
Wetness is an important problem for stamps. Some collectors will put stamps in separate plastic (塑料) bags. However, it is possible that some stamps have taken in some water from the air before they are put into the plastic bags. Stamps become yellow easily and rapidly after they take in wet air. To protect the stamps, some people also put the stamps into a special room which has a machine to keep the air cool and dry. However, not many people can afford that.
