Which of the following groups consists of only homeothermal animals/warm blooded animals?

Correct answer, all are homeothermic animals. Vertebrates show lot of variations as we move up in their hierarchy, i.e., moving from fishes to mammals.Their habitat changes from water to land to air, similarly they exhibit changes in their nutrition, survival traits, reproduction etc.While combating various types of environments vertebrates also learnt to regulate their own body temperatures to face weather extremes. Some of them could not do so are now called cold-blooded animals(body temp. varies with environment) e.g. fish, amphibians, reptiles. While those who could regulate are called warm-blooded animals e.g. birds,mammals. Humans, dogs, cats, bears, lions, most types of birds, and horses are some examples of a warm blooded animal. These animals have the ability to maintain their body's temperature, no matter what type of environment they are in. They are not dependent on the environment to heat or cool their bodies, in other words.