英语阅读理解,急Today,air travel is far safer than driving a car on

英语阅读理解,急
Today,air travel is far safer than driving a car on a busy motorway.But there is a danger that grows every year.Airliners get larger and larger.Some can carry over 300 passengers.And the air itself becomes more and more crowded.If one large airliner crashed(撞) into another in mid-air,600 lives-could be lost.
From the moment an airliner takes off to the moment it lands,every moment it is watched on radar(雷达) screens.Air traffic controllers tell the pilot exactly when to turn,when to climb and when to come down.Any plane that flies near the airport comes under the orders of the controllers there.Even a smaller mistake on their part could cause a disaster(灾难).Recently such a disaster almost happened.Two large planes were flying towards the airport.One was carrying 69 passengers from Toronto.The other was carrying 176 passengers from Chicago.An air traffic controller noticed on his radar screen that the two planes were too close to each other.He ordered one to turn to the right and to climb.But he made a mistake.He ordered the wrong plane to do this.So,instead of turning away from the second plane,the first plane turned towards it.Fifteen seconds later it flew directly in front of the second plane.They avoided(避开) each other by smallest part of a second.The distance between them was less than that of a large swimming pool.This is an example of the danger that grows every year.
How many example of the danger did the writer take in the passage?

one.
开头的But there is a danger that grows every year.
和结尾最后一句This is an example of the danger that grows every year.
都表明了.
整篇文章开头点明了这种危险的存在,在第二段中,引用真实例子来说明.