Proteins are: a. Resistible to structural changes.
b. Polymers of amino acids bound by peptide bonds.
c. Have different structures but same function.
d. All hydrophilic​

Hello there!

Proteins are created by the bonding of amino acids. The bonds are called peptide bonds.

So the answer must be b.

I hope this helps!! :)

air enters through the nose, moves through the nasal cavity, the pharynx, the larynx, enters the trachea, moves through the bronchi andbronchioles till the alveoli.