What’s a kiva? In American history

Kiva, subterranean ceremonial and social chamber built by the Pueblo Indians of the southwestern United States, particularly notable for the colourful mural paintings decorating the walls.

A Kiva is a special sacred building, usually built underground, that is used for spiritual ceremonies, religious rituals and ceremonial preparations by the Pueblo Native Americans and strongly associated with the Kachina belief system.

Explanation:

a. theta waves. this is because the person is in a light sleep which means the brain waves would show these kind of waves.