7 . The idea that red means stop and green means go has impacted our lives in more ways than just traffic signals. We have been taught from a young age that the color red means danger and green means it’s okay to move forward. But why were those particular colors chosen for traffic lights in the first place? For something we have to look at every day, why couldn’t they have been prettier colors like magenta and purple?
Well, it’s important to know that before traffic lights for cars even became a thing, there were traffic signals for trains. At first, railroad companies used red to means top, white to mean go, and green to mean caution. As you could imagine, train conductors ran into a few problems with white meaning go. For instance, one train conductor mistook a bright star for a white light and thought he was all clear. Well, as you can imagine, an accident occurred. Because of common incidents like that, railway companies eventually proposed green meaning go, and it’s been that way ever since.
As far as red goes, that’s always been a color that indicated danger, long before cars were even around. This most likely started because it’s the color with the longest wavelength so it can be seen from a greater distance than other colors.
As far as yellow goes, it was used to caution drivers because it has a slightly shorter wavelength than red, but not as short as green.
But, believe it or not, yellow was once used to means top the flow of traffic, at least as far assigns go. Back in the 1900s, some stop signs were yellow because it was too hard to see a red sign in a poorly lit area. Eventually, materials were developed that were highly reflective and red stop signs were born. Since yellow can be seen well at all times of the day, school zones, some traffic signs, and school buses continue to be painted yellow.
1. What does the underlined word “clear” mean in the second Paragraph?
| A．Without doubt. | B．Easy to understand. | C．Cloudless in the sky. | D．Free from dangers. |
2. Which of the following colors has the longest wave?
| A．Purple. | B．Yellow. | C．White. | D．Red. |
3. Which of the following events came last?
| A．Traffic signals for trains came into being. |
| B．Railway incidents happened frequently. |
| C．Yellow is widely used for its special character. |
| D．Railway companies chose green meaning go. |
4. What’s the purpose of the author’s writing this passage?
| A．To entertain. | B．To inform. | C．To persuade. | D．To advertise. |
