<span>d. All of the above
These behaviors;
Spreading wings
Flattening feathers
panting
are all evolutionary process to maintain body temperature. Birds are warm-blooded animals. Also known as </span><span>homeotherms, which is defined as having the constant body temperature. This is a vital function for the survival of the specie.
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<span>c. are hollow
</span>
The bones of most birds are hollow in order for the weight of the birds to be light for them to fly.
A large class of molecules is called a macromolecule.
