Proteins are composed of what smaller subunits? amino acids
fatty acid
nucleotides
nucleic acids

/the trachea, commonly known as the windpipe

"a.) well–developed vascular system."

b is the answer and if you need further with anything message me

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.