题目内容：

阅读下面材料，在空白处填人适当的内容（1个单词）或括号内单词的正确形式。将答案填写在答题卡的相应位置。

The History of Air Conditioners

The first practical cooling system for use in industry   1.   (invent) in 1902 by Willis Carrier in New York, the USA. He continued to improve  2.   （he) invention and, in 1928, developed the first air conditioner for home use. In 1939, an American car company introduced the first air conditioner for cars,   3.   (make) driving more comfortable.

After World War II many American  4.    (company) began making air conditioners and, beginning in 1950, many homes in the USA were equipped 5.    central air conditioning. Central air conditioning uses a single unit6.   （heat) or cool a whole house. With this, people could escape the heat of summer and the cold of winter no matter    7. they were in the house.

In the 1970s, electricity 8.    （become) more expensive, so people developed    9.(good) air conditioners to save money. Later, the cooling gas in air conditioners was found to pollute the environment, so engineers have been working to produce air conditioners more friendly to the environment  10.   the 1980s.