Question

What is the size of an alveoli?

Answer 1

`200` micrometers

Explanation:

An average sized alveolus in an adult human being is around `200` micrometers long. In the human lungs, there are about `70` million alveoli, combining for a total of `70 \ "m"^2` of surface area for efficient gas exchange.

Source:

https://en.wikipedia.org/wiki/Pulmonary_alveolus