Geographic barriers can influence groups of people to form cultures in isolation because they prevent the influence of outside factors.
a. true
b. false

This is True. Examples of this could be cultures of various tribes on islands that formed their culture without the influence of outside factors before being discovered.

Sequoia national park  /  inyo national forest, california, u.s. mount whitney is the tallest mountain in california, as well as the highest summit in the contiguous united states and thesierra nevada—with an elevation of 14,505 feet (4,421 m).