A、Because both farmers and scientists try to make weather forecast. B、Because people in all countries make weather forecast. C、B

Not only farmers but also scientists have studied weather forecasting. People for many centuries and in all countries have studied the weather and tried to make weather forecast. Sometimes distant objects such as hills and tall trees seem to be very clear and near. This is a sign of much water in the air, and therefore rain will probably come. When distant sounds, such as noise from a train, birds singing, people shouting, are very clearly heard, then wet and stormy weather is on the way. (30)Some birds, particularly swallows, fly high if fine weather is coming, but they fly very near the ground if rainy weather or a storm is on the way. This is because probably the insects, which they are hunting, then fly low. (31)If you see a rainbow during rainy weather, this is a sign that the weather will clear up and become fine. Such rainbows always come in the evening. If the stars twinkle-clearly at night, then fair weather will continue. If a mist appears in the early morning, just about sunrise, then the day will be warm. If the sunset is mostly red in color, then the following day will be fine. When big clouds disappear at sunset, then the weather will follow on the next day. (32)If a rainbow appears in the morning, then rainy weather will probably come. Most of the above sayings have been made up by people who have used their eyes and their brains to forecast the weather.