Feathers are modified
a. scales
c. lipids
b. hair
d. tibia

there is not 1 highest source of protein, but there are many; meats, fish, poultry, seafood, cheese, eggs, yogurt and milk. the only non complete animal food that is beneficial is gelatin.

sorry if this did not , have a great day!

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.