Question

this grapelike out-pouching lined with epithelium and supported by a thin, elastic basement membrane is the site where gas exchange occurs in the lungs.
lobule
alveolus
bronchiole
trachea

Explanation:

The description refers to the tiny, grapelike air sacs in the lungs that are the primary site of gas exchange, lined with epithelium and supported by a thin basement membrane. Lobules are larger lung divisions, bronchioles are small air-conducting tubes, and the trachea is the main windpipe, none of which match the given description.

Answer:

Alveolus