How do the feathers of the bird keep it warm in cold weather?

The feathers of a bird keep the bird warm in cold weather as the bird's body heat warms the air between its feathers. The more trapped air, the warmer the bird will be. Their legs are kept warm as they stand on one leg whilst one is tucked up into the feathers of the birds stomach, keeping it warmer.

-Hope it helps! xo

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

i wanna say it’s between b and d, leaning more towards b.