52．On 19th September 1783，Pilatre De Rozier，a scientist，sent the first hot air balloon．The passengers were three animals and the balloon stayed in the air for about 15 minutes before hitting back to the ground．
The first manned（載人的）flight was about 2 months later，with a balloon made by 2 French brothers．The balloon flew for a period of 20 minutes．
Sailing through the sky in the balloon，high above buildings and trees，you can't feel or hear the wind because you're traveling in the same direction and at the same speed as it is．
A hot air balloon has three main parts：the balloon，called an envelope；a basket，where passengers ride；and a burner system，which supplies the hot air．
Most balloon envelopes are made of strong，lightweight nylon（尼龍）．They are different in size and shape，but they have to be really，really big to lift even one person．Most weigh more than an adult man．
The basket is usually made of wicker（柳條），which is strong but not too hard．It needs to bend a bit for a soft landing，just like a good jumper bends her legs instead of keeping them straight when she lands．
The hot air balloon works on the theory that hot air rises faster than cooler air．When the burner system is turned on，it makes a noisy sound，but once the balloon is flying，the burner can be turned off．The air in the envelope will then cool，and the balloon will slowly go down unless the pilot starts the burner system again．
To control a hot air balloon，a pilot adds hot air to it to go up or lets the air out to go down until he finds a wind blowing in the direction he wants to fly．But no matter which way the wind blows，the passengers have an amazing bird's-eye view of the world．
64．Who were the passengers on the first hot air balloon？
65．Did the first manned balloon fly for 20 minutes？
66．Why is the basket usually made of wicker？
67．How does a pilot control the hot air balloon？
68．What are the main points in this passage？
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