Passage Three 　　
There are many ways to learn about people of other lands. One way is to study the clothing other people wear. 　　
For thousands of years, people in different parts of the world have worn very different types of clothing. There are four big reasons for this. 　　
One reason might be religion. In many Moslem countries, women must wear veils (面纱) to hide their faces. The veils must be worn in public. Veils are part of the Moslem religion. The second reason is that different materials are used in different countries. For instance, in France the materials used in clothing may be cotton, silk, wool, or many other man-made materials. Most people in China wear cotton. 　　
The ways clothes are made are also very different. This is another reason why people dress differently. Western countries rely on machines to make most of their clothing. Someone living in India can use only hand power to make the clothing he needs. 　　
Worldwide differences in customs also lead to differences in clothing. A Mexican farmer wears a straw hat with a brim (帽沿) up. In China, a farmer wears a straw hat with a brim down. Both hats are used to protect the farmers from the sun. Some of these customs have come down through thousands of years.

Which of the following is the reason for the differences in clothing（）