单选题 Passage Three
Questions 33 to 35 are based on the passage you have just heard.
单选题
  • A. Sense of color.
  • B. Sense of smell.
  • C. Either sense of color or smell.
  • D. Both sense of color and smell.
【正确答案】 B
【答案解析】[解析] 33-35 Dog is known as man's best friend. But do you know our best friend is colorblind? Fortunately, his survival does not depend upon the ability to see colors. (33){{U}}His keen sense of smell makes up for his inability to see colors, and enables him to differentiate between things.{{/U}} Extensive scientific testing on dogs supports the conclusion that they live in a colorless world. (34){{U}}The testing done primarily focused on the dogs' responses to colors for food. Dogs could not tell the difference between one color, a signal for food, and other colors, that were not for food.{{/U}} Similar tests conducted on cats produced similar results, which led scientists to conclude that they, too, are colorblind and live in a gray world. The inability of most animals to see colors, from an evolutionary standpoint, is quite simple to understand. Many colorblind animals have dull-colored coats, hunt for food in the dark of night, or graze in the dim twilight hours. (35){{U}}Their other senses have developed to the point where the lack of color vision in no way affects them. For them, life in a colorless world is neither a handicap, nor a threat to their survival.{{/U}} The only animals, other than man, scientists can conclusively say have color vision are monkeys and apes. Both can be trained to open a colored door, behind which is food, and man can be trained to open a refrigerator door of any color! Q: What enables dogs to recognize different things? [一点即通] 本题关键句为His keen sense of smell makes up for his inability to see colors, and enables him to differentiate between things. 可知狗的敏锐嗅觉弥补了它们看不到颜色的缺陷，使它们可以分清事物。故B)项正确。
单选题
  • A. Dogs can not recognize the connection between color and food.
  • B. Dogs can not understand signals for food.
  • C. Dogs can not give responses to the color of food.
  • D. Dogs can not tell the differences in the meaning of colors.
【正确答案】 A
【答案解析】[解析] Q: How does the testing find that dogs are colorblind? [一点即通] 本题关键句为The testing…Dogs could not tell the difference between one color, a signal for food, and other colors, that were not for food. 可知研究发现狗不能区分代表食物的颜色和不代表食物的颜色，即不能辨认颜色和食物的联系。故A)项正确。
单选题
  • A. It is a handicap for them.
  • B. It is not good for their survival.
  • C. It is good for their hunting.
  • D. It does not harm for their hunting.
【正确答案】 D
【答案解析】[解析] Q: How do we understand the inability of most animals to see colors? [一点即通] 本题关键句为…where the lack of color vision in no way affects them…可知不能分辨颜色并不影响这些动物的正常生活。故D)项正确。