【正确答案】正确答案： Tornadoes A tornado is a violently turning tube of air suspended from a thick cloud. / It extends from a thunderstorm in the sky down to the ground. / The shape is like a funnel: / wide at the top, narrower at the bottom. / Tornadoes form when winds blowing in different directions / meet in the clouds and begin to turn in circles. / Warm air rising from below causes the wind tube to reach toward the ground. / Because of their circular movement, / these windstorms are also known as twisters. / The most severe tornadoes can reach wind speeds of 320 kilometers an hour or more. /