Surfactant:
a) is produced by pneumocytes type i.
b) phagocytizes dust or debris.
c) replaces mucus in the alveoli.
d) plays a key role in keeping alveoli open.
e) is not found in healthy lung tissue.

The correct answer will be option-D

Explanation:

Pulmonary Surfactant is a complex substance produced by the pneumocytes epithelial II cells in the alveolar sac.

The surfactant is composed of the proteins and lipids which plays a role in keeping alveoli open by reducing the surface tension formed between the air and liquid.

The surfactant act by forming a monolayer surface film which helps reduce the surface tension.

Thus, option-D is the correct answer.

tissue

explanation:

it is actually formed by geoup of cells which is tissue

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.