This is located anterior to the esophagus and carries air to the bronchi.

a.trachea
b.larynx
c.nasopharynx
d.pharynx
e.none of the above

The correct answer is: a.Trachea

Respiratory system or respiratory tract is divided into upper and lower tract. Upper respiratory tract includes nose and its cavities, sinuses, pharynx and the part of the larynx. Lower respiratory tract consists of the trachea (a cartilaginous tube that connects the pharynx and larynx with the two bronchi), bronchi, bronchioles and the alveoli. Alveoli are the small folded air sacs, the ends of the respiratory tract and the smallest units in it. They provide an extremely large surface area for the gas exchange. Gas exchange occurs thanks to small blood vessels – capillaries that surround alveoli and it occurs via the process of diffusion.