（贵州省兴义九中09-10学年高三上学期期中考试）

C

From the coldest arctic ice to the hottest deserts you will find mammals living and thriving（兴旺）. There seems to be no climate that they can’t adapt to , however changeable it may be. Why can mammals adapt to so many different habitats? There is a good reason for this – mammals have the ability to keep their body at a constant temperature whatever the weather. They are “warm-blooded”

Mammals achieve this by chemically “burning” their food as fuel inside their bodies. This is kept under tight control by a region of the brain that acts like a thermostat（恒温器）, and this makes sure that the mammal’s body temperature stays about the same.

A constant body temperature is a great advantage for mammals because all the chemical processes that go on inside a living body are likely to happen more slowly at low temperatures and faster at higher temperatures. Mammals can regulate their temperature at the best condition for all these processes, allowing them to be active at very cold or very hot periods and to keep up tiring activity for a long time. Animals such as lizards（蜥蜴）rely on moving in and out of the warm sunlight to regulate their body temperature. They slow down when they can’t warm up and may die if they can’t get away from heat. They also tend to overheat quickly when they are active as their muscles produce warmth.

Using food energy to keep body temperature constant is expensive, and since mammals need to be efficient at keeping to warmth they create inside themselves, they often have fur and a cover of fat under their skin to prevent heat from escaping. To help lose heat when they are too hot, they have sweat glands（汗腺）that take the heat away from the skin through evaporating（蒸发）water. This means, though, that they need to drink more than other animals.

64．Mammals can adapt to so many habitats because          .

       A．the climate is unchangeable                  

B．they can regulate their body temperature

       C．they are “warm-blooded”                     

D．their muscles produce warmth

65．When mammals keep their body at a constant temperature,          .

       A．the chemical processes happen more slowly in their bodies

       B．the chemical processes happen faster in their bodies

       C．they will use less fuel inside their bodies

       D．they can live an active life

66．We can infer from the last paragraph that mammals         .

       A．need to drink more than other animals

       B．have different ways of keeping their body temperature

       C．often have fur and fat to prevent heat from escaping

       D．have sweat glands that take the heat away from the skin

67．The writer answers the question raised in the first paragraph with          .

       A．stories and explanation                         B．examples and conclusion

       C．evidence and argument                         D．explanation and comparison