We often see wind-horse flags in Tibetan areas. They are long cloths on which pictures of horses and scriptures are printed. People often put these flags on top of houses, or leave them where a vehicle accident happened. They prevent evil spirits from injuring people again. A wind-horse flag can be white, yellow, red, green or blue. These five colors symbolize the five elements that form the world; earth, water, fire, wind and sky. Another explanations that red is the sun, green is the grassland, yellow is the earth, blue is the sky, and white is the cloud. The wind-horse flag originated with a monk who obtained a scripture from India. When he crossed a river, he carelessly dropped the scripture into the water. He quickly saved the scripture and spread it out on a big rock to dry as he sat in meditation . Suddenly violent thunder sounded like drums. The monk felt liberated from all of his sadness, and when he opened his eyes he saw that the scripture had been blown into the sky by a strong wind. Finally, he went straight to heaven. In order to honor the spirit of the monk and the Buddhist scripture, people printed the scripture on a piece of cloth and hung it up between the sky and the earth as though the scripture was flying in the sky. We also know why people put the wind-horse flag on the top of mountains and houses. The Tibetan ancestors had a very great idea about chanting scripture. They thought people not only could chant scripture, but also the five elements. The wind-home flag is a good example of how they use the wind to blow the flag, which means that the wind also chants scripture. According to the passage, the origin of the wind-horse flag is based on   _  .
a historical event an ancient custom a religious tale a vehicle accident
Question: We often see wind-horse flags in Tibetan areas. They are long cloths on which pictures of horses and scriptures are printed. People often put these flags on top of houses, or leave them where a vehicle accident happened. They prevent evil spirits from injuring people again. A wind-horse flag can be white, yellow, red, green or blue. These five colors symbolize the five elements that form the world; earth, water, fire, wind and sky. Another explanations that red is the sun, green is the grassland, yellow is the earth, blue is the sky, and white is the cloud. The wind-horse flag originated with a monk who obtained a scripture from India. When he crossed a river, he carelessly dropped the scripture into the water. He quickly saved the scripture and spread it out on a big rock to dry as he sat in meditation . Suddenly violent thunder sounded like drums. The monk felt liberated from all of his sadness, and when he opened his eyes he saw that the scripture had been blown into the sky by a strong wind. Finally, he went straight to heaven. In order to honor the spirit of the monk and the Buddhist scripture, people printed the scripture on a piece of cloth and hung it up between the sky and the earth as though the scripture was flying in the sky. We also know why people put the wind-horse flag on the top of mountains and houses. The Tibetan ancestors had a very great idea about chanting scripture. They thought people not only could chant scripture, but also the five elements. The wind-home flag is a good example of how they use the wind to blow the flag, which means that the wind also chants scripture. According to the passage, the origin of the wind-horse flag is based on   _  .
A. a historical event
B. an ancient custom
C. a religious tale
D. a vehicle accident
Answer: