The walls of the alveoli are composed of two types of cells, type i and type ii. the function of type ii is to a. trap dust and other debris b. protect the lungs from bacterial invasion c. replace mucus in the alveoli d. secrete surfactant

D. secrete surfactant

Explanation:

The function of the alveolar type II cells is to secrete a lipoprotein material which is known as surfactant. The primary function of this surfactant is to reduce surface tension in alveoli.

Surfactant is a type of lipoprotein which is consisting of mainly and some glycoprotein components. The material spreads out over surface of alveoli and thereby, reducing the surface tension by interaction of the hydrophilic parts of surfactant molecule with the water layer next to alveolar cells and by interaction of hydrophobic parts of surfactant with air.

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