阅下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。 When ___41___ (drive), we will stop when the traffic lights turn red

阅下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
When ___41___ (drive), we will stop when the traffic lights turn red. Why do we use red instead_____42_____ other colors?
Of all of the visible lights, red____43____(have) the longest wavelengths about 1.7 times that of purple. So the scattering is the_____44_____(weak). That means red light travels far. In fact, it travels farther on rainy or foggy days because of the reduced air transparency.
Using red lights as a stop signal helps drivers in more remote areas see the signal. It helps drivers slow down or brake in time. If drivers didn't see the stop signals until they____45____(be) close, they might not be able to stop the car in time,____46____ (possible) causing an accident. Red is also a color____47____ excites people, and the visible nerve especially responds to red. In short, red lights help drivers stop in time and help prevent___48___(accident).
Red lights are not only used as stop signals but also warnings. For example, red lights are installed on_____49_____ tops of tall buildings in cities so that pilots in aircraft can clearly see them at night. Red lights are also_____50_____ (use) for public security and fire department vehicles
【答案】41. driving    
42. of    43. has    
44. weakest    
45. were    46. possibly    
47. that/which    
48. accidents    
49. the    50. used
【解析】
这是一篇说明文。文章主要解释了红色被用作交通灯的原因，因为红色最不容易被散射且能使人兴奋，所以红灯帮助司机及时停车，防止事故发生。还介绍了红色在其他方面的应用。
【41题详解】
考查省略句。句意：开车的时候，我们会在交通灯变红的时候停下来。when引导状语从句时，常省略和主句相同的主语，和从句中的be动词，从句描述正在发生的动作，应用现在进行时，完整为when(we are) driving。故填driving。
【42题详解】