Every animal is a living radiator-heat formed in its cells(细胞), which gives off heat through its skin. Warm blooded animals keep a normal temperature by continuously replacing lost surface heat; smaller animals, which have more skin for every ounce(盎司) of body weight, must produce heat faster than bigger ones. Because smaller animals burn fuel faster, scientists say they live faster.

　　The speed at which an animal lives is determined by measuring the rate at which it uses oxygen. A chicken, for example, uses one-half cubic(立方) centimeter of oxygen every hour for each gram it weighs. The tiny shrew-mouse uses four cubic centimeters of oxygen every hour for each gram it weighs. Because it uses oxygen eight times as fast, it is said that the shrew-mouse is living eight times as fast as the chicken. The smallest of the warm blooded animals, the hummingbird, lives a hundred times as fast as an elephant.

　　There is a limit to how small a warm-blooded animal can be. A mammal or bird that weighed only two and a half grams would starve to death. It would burn up its food too rapidly and would not be able to eat fast enough to supply more fuel.

　　1. The passage says that every animal is a living radiator because it _______.

　　A. produces heat in its body cells B. burns fuel to produce heat

　　C. gives off heat through its skin D. requires oxygen to produce heat2. Small animals are said to live faster than big ones because they _______.

　　A. have more skin for their body weight B. replace lost heat faster

　　C. burn fuel faster D. keep a higher body temperature

　　3. The amount of oxygen an animal uses depends on _______.

　　A. its body weight B. the food it eats C. its general size and shape D. the length of time it lives

　　4. Which of the following can be inferred from the passage?

　　A. There is no limit as to how large a warm blooded animal can be

　　B. The hummingbird lives faster than any other warm-blooded animal

　　C. Small animals have less skin for their body weight than large ones

　　D. The hummingbird is the smallest of the warm-blooded animals

　　(1—4 CCAB)

　　【答案解析】本文是说明文，阐述了热血动物的体积与所耗热量，动物生长速度与用氧速度之间的关系。

　　1. C。细节题。根据 heat formed in its cells is given off through its skin 可推知此题答案为C。

　　2. C。细节题。根据Because smaller animals burn fuel faster, scientists say they live faster.可得出答案。

　　3. A。推断题。根据A chicken, for example, uses one-half cubic centimeter of oxygen every hour for each gram it weighs. The tiny shrew-mouse uses four cubic centimeters of oxygen every hour for each gram it weighs. 可见耗氧量与动物体积有关。

　　4. B。推断题。前面说到动物生长速度决定于用氧的速度，而用氧量与动物体积有关，而hummingbird是最小的热血动物，故可得出答案B。

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