Traffic lights are red, yellow and green. They are very important signals (信号). Traffic lights are usually placed at busy street corners to help control traffic Sometimes, they are on streets near schools and shops, too. Most young children are taught what each of the colored lights means, so everybody can stay safe.
The first traffic signals were used for trains. The signals were put alongside railway tracks ( (轨道). The color red was used to mean "stop" because it warned people of danger. A red light was also the easiest color to see from a distance. Train drivers could see the red "stop" light ahead and had enough time to slow down and stop their trains. A green light was used to mean "take care" and a white light meant "go".
However, there were many dangerous accidents on the train tracks. Some train drivers thought a star shining in the night sky was a white light that meant "go"". So the signals were swapped. The "go" light was changed to green and the "take care" light was changed to white.
During these times, people travelled by train or in carts pulled by horses. Years later, when cars were built, people began to drive them because they could travel much faster than horses. However, the road rules for drivers were not very clear and many people were hurt crossing the roads. Yellow warning signs had to be placed beside the roads to remind drivers to take care and allow people to cross safely.
Today, towns and cities all over the world have traffic lights. Red and green lights match the signals used on the railways. Yellow lights are easy to see, so they are used to warn drivers that they should slow down and prepare to stop.
19. Why was the color red used to mean "stop"?
A. It reminded people of traffic rules.
B. It helped trains run smoothly.
C. It gave people a warning of danger.
D. It was the first color people thought of.
20. What does the underlined word "swapped" in Paragraph 3 mean?
A. Designed. B. Exchanged. C. Suggested. D. Compared.
21. In which order did the "take care" light develop?
a. A white light b. A green light. c. A yellow light.
C. a一c一b B. b一c一a A. a一b一c D. b一a一c
22. What is the passage mainly about?
A. The advantages of traffic lights. B. The history of traffic lights.
C. The importance of traffic lights. D. The meanings of traffic lights.
CBDB
文章大意:本文主要讲述了红绿灯的发展由来一一从火车上的演变到今天马路上能见到的交 通信号灯。
1. 事实细节题。根据第二段第三句 The color red was used to mean "stop" because it warned people of danger可知，火车使用红色的标志牌是想警告人们危险。C选项“它 给人们以危险的警告”与原文意思相符，故选C。
2. 词义猜测题。根据第二段最后一句 A green light was used to mean "take care" and a white light meant “go”可知，绿灯意味着小心，白灯意味着通行。而第三段swaped 后的一句话 The "go" light was changed to green and the "take care" light was changed towhit e可知，绿色信号灯和白色信号灯的寓意交换变换发生了改变。A选项 意为“设计” ；B选项意为“交换”；C选项意为“建议” ；D选项意为“比较”。故 选B
3. 事实细节题。根据第二段 A green light was used to mean "take care”；第三段 the "take care" light was changed to white； 第四段 Yellow warning signs had to be placed beside the roads to remind drivers to take care, 可知，"take care" light 的发展过程由绿色到白色再到黄色，对应的正确的排序为b-a-c,故选D。
4. 主旨大意题。由第二段开头 The first traffic signals were used for trains；到 第四段开头 During these times. .. Years later...；到最后一段开头 Today...,可知 文章以时间轴的顺序在介绍红绿灯的发展由来一从火车上的演变到今天马路上能见到 的交通信号灯，也即交通信号灯的历史，故选B。
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