What is the main idea of the passage?

Câu hỏi: Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.
Throughout history, various people have demonstrated a high degree of confidence in the ability of certain animals to predict the weather. It may seem surprising today in view of the complex equipment now involved in weather forecasting to understand that in certain cases, the behavior of animals does indeed provide an indication of inclement weather. Sensitivity of certain animals to falling air pressure or to low-frequency sound waves that humans cannot hear, which are indicators of approaching storms, causes behaviors in animals that certain societies have come to recognize as predictors of storms.
A number of animals are remarkably sensitive to variations in air pressure, and some of these animals show consistent, noticeable, and predictable behaviors as air pressure drops before a storm hits. Where the air pressure drops before a storm, some animals move closer to the ground to equalize the pressure in their ears: some birds such as swallows tend to stay on the ground or roost in trees instead of soaring in the skies when a storm is imminent because of the decreasing air pressure. Other animals make more noise than usual as air pressure drops: an unusual amount of quacking by ducks and a high volume of croaking by frogs are both indicators that are believed to occur because of the high degree of sensitivity of ducks and frogs to the change in pressure. Finally, still other animals become more active before storms as a reaction to the falling air pressure: dolphins and porpoises seem to be taking part in a frenzied sort of play, and bees and ants become more active prior to storms, most likely because of their sensitivity to lower pressure.
There is good reason to believe that the fact that these animal behaviors seem to occur regularly prior to storms may have a scientific basis and that the animals demonstrating these behaviors may actually be good short-range weather forecasters. However, their ability to predict long-range weather patterns is rather suspect. Certain proverbs, for example, are based on what is most likely the idea that squirrels are good indicators of long-range weather patterns. One proverb indicates that, if a squirrel seems busier than usual in gathering nuts, then a long and cold winter is on its way; however, this behavior in squirrels is more likely due to a large supply of nuts available for gathering, which occurs because of earlier good weather, and is not an indicator of cold weather to come. Another proverb about squirrels indicates that if a squirrel grows a long and bushy tail in the fall, then a particularly harsh winter is on its way; in this case too, the squirrel develops a long and bushy tail because of earlier good weather and not as a warning of bad weather to come.
(Adapted from TOEFL Reading Practice by Deborah Philips)
What is the main idea of the passage?
A. Animals as weather forecasters.
B. Signs of a weather condition.
C. Proverbs of weather.
D. Study of animal behaviors.