The burner uses propane gas to heat up the air in the envelope to move the balloon off the ground and into the air. The pilot must keep firing the burner at regular intervals throughout the flight to ensure that the balloon continues to the stable. Naturally, the hot air will not escape from the hot at the very bottom of the envelop as firstly, hot air rises and secondly, the floating power keeps it moving up.
To move the balloon upwards, the pilot opens up the propane value which lets the propane flow to the burner which in turn frees the flame up into the envelope. It works in much the same way as a gas grill: the more you open the valve, the bigger the flame to beat the air and the faster the balloon rises.
The “Parachute Valve” at the very top of the balloon is what is used to bring the balloon down towards the ground. It is a circle of fabric cut out of the top of the envelop which is controlled by a rope which runs down through the middle of the envelope to the basket. If the pilot wants to bring the balloon down, he or she simply pulls on the rope which will open the valve, letting hot air escape, decreasing the inner air temperature. This cooling of air causes the balloon to slow its rise.
The pilot can operate horizontally by changing the vertical position of the balloon because the wind blows in different directions at different altitudes. If the pilot wants to move in a particular direction, he or she simply arises and falls to the appropriate level and rides with the wind. 60. The purpose of this article is to __________. A. explain how hot air balloons work. B. illustrate why hot air balloons are useful. C. describe hot air balloons’ structure.
D. inform readers about how hot air balloons are made.
61. What would happen if the “Parachute Valve” could not be released after it was opened? A. The inside of the balloon would continue to heat up. B. The balloon would climb up more rapidly.
C. The self-sealing valve would need to take over the role of the Parachute Valve. D. The balloon would begin to move down more rapidly.
62. Which of the following skills or knowledge would be the most useful to a balloon pilot? A. The ability to sew the panels of fabric together to make a balloon. B. An understanding of how propane gas is manufactured.
C. A knowledge of the background of passengers who are travelling in the balloon.
D. A knowledge of air currents and wind directions in the area where he is piloting the balloon. 【答案】60. A 61. D 62. D 【解析】 【分析】
这是一篇说明文，介绍了热气球的构造以及其工作原理。 【60题详解】
推理判断题。由第一段“The basis of how the balloon works is that warmer air rises in cooler air.第二段The burner uses propane gas to heat up the air in the envelope to move the balloon off the ground and into the air.第三段To move the balloon upwards, the pilot opens up the propane value which lets the propane flow to the burner which in turn frees the flame up into the envelope第四段The “Parachute Valve” at the very top of the balloon is what is used to bring the balloon down towards the ground第五段The pilot can operate horizontally by changing the vertical position of the balloon because the wind blows in different directions at different altitudes.”可知，每一段都在介绍热气球的是怎么工作的，所以短文的目的就是在介绍热气球是怎么工作的。故A选项正确。
【62题详解】
推理判断题。由最后一段“The pilot can operate horizontally by changing the vertical position of the balloon because the wind blows in different directions at different altitudes. If the pilot wants to move in a particular direction, he or she simply arises and falls to the appropriate level and rides with the wind.”可知，飞行员可以通过改变气球的垂直位置来水平操作，因为风在不同的高度向不同的方向吹。如果飞行员想朝某一特定方向移动，他或她只需站起来
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