Question

Birds and mammals share one of the following characteristics as a common feature.
(a) Pigmented skin
(b) Pneumatic bones
(c) Viviparity
(d) Warm blooded

Answer 1

Hint: Birds and mammals show homeostasis, i.e., maintenance of body temperature. Animals respond to a wide range of temperatures by physiological changes in their body. Those animals whose body temperature changes with variation to surrounding environmental temperature are called cold blooded animals and those whose body temperature does not change with variations to surrounding environmental temperature are called Warm blooded animals.

Complete answer
The first option is pigmented skin which is not seen in both the birds and mammals. Birds have feathers around their body and mammals have hairs on their body. Pigmented skin is rarely found in mammals.
The second option is pneumatic bones which is a characteristic feature of birds. Pneumatic bones are hollow and have an air filled cavity due to which they are of light weight which makes them easy to fly whereas in mammals there is no such character present.
The third option is Viviparity which is a characteristic feature of mammals. Viviparity is the process by which mammals give birth to young ones whereas birds do not show Viviparity because they lay eggs. Hence, they are oviparous. Most mammals are viviparous but there are egg laying mammals also which are seen in Platypus. Thus Viviparity is not a common feature in birds and mammals.
The fourth option is warm blooded which is one of the common characteristics seen in birds and mammals. Warm blooded animals are those animals which maintain a constant body temperature, regardless of temperature variations of the atmosphere. They are also called Homeotherms. Both birds and mammals are able to maintain their body temperature in summer and winter. They are able to maintain constant body temperature by several methods, such as by a thermoregulatory center in the brain, insulation or metabolic compensation.

So, the correct answer is ‘Warm Blooded’.

Note:
Mammals are considered to be the most successful organisms on this earth because of their ability to maintain a constant body temperature in the rigid Antarctica as well as the high temperature of the Sahara desert.