Assertion : The birds can maintain a constant body temperature.
Reason : Birds possess feathers covering their body

Options

A. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
C. If the assertion is true but the reason is false
D. If both the assertion and reason are false

Answer

A

Explanation

Birds have a constant body temperature which commonly remains in between `104^(@)` to `112^(@)`F, ever in subzero weather. Thus they are called homoiothermal. The feathers serve the most important function of retention of heat. Because the plumage form an efficient, non-conduction covering with its innumerable dead air spaces, useful as insulation. In cold weather, the heat loss is reduced to minimum by fluffing out the feathers, which increase the depth of insulating material by adding to the air spaces within the feathery layers. In warm weather, the feathers are often held close to the body to allow some escape of body heat.