单选题 　　About nine men in every hundred 61 from color blindness in some way; women are luckier—only about one in two hundred is affected in this manner. Perhaps, after all, it is safer to be driven by a woman. There are different forms of color blindness. In some cases, a man may not be able to see deep red. He may think that red, orange and yellow are shades of green. Sometimes a person cannot 62 the difference between blue and green. In 63 cases, an unlucky man may see everything in shades of green--a 64 world indeed. Sometimes color blindness can be dangerous. For example, when in the forest 65 soldiers use 66 to signal to 67. A green light may mean" 68 "and a 69 light may mean "Danger, keep back." You can seen what will 70 if somebody thinks that is green.