2. Warm-blooded animals control their internal body temperature through their metabolism. This means that they convert food into energy, which is then used to keep their bodies at a more-or-less constant temperature. For example, humans maintain a normal temperature of around ninety-seven degrees Fahrenheit. When the weather is too hot, warm-blooded animals sweat to cool their bodies. When the weather is too cold, they may consume more food to burn more energy, or they may shiver to increase muscle activity, which will produce more heat. Some warm-blooded animals maintain constant high metabloic rates so that they can sustain their body temperatures in all environments. Additionally, warm-blooded creatures that dwell in very cold environments tend to have greater external protection. This may manifest itself in the guise of fur, hair, and feathers. Humans also wear clothing for protection; the colder the temperature, the thicker the clothing.
Q : The author discusses shivering in paragraph 2 in order to
A : give an example of an activity that cold-blooded animals cannot do
B : explain how warm-blooded animals may warm themselves in the absence of food
C : describe a common muscle activity that all kinds of animals may engage in
D : show how warm-blooded animals can maintain high metablolic rates in their bodies