How Does Peak End-Expiratory Pressure (PEEP) Assist a Ventilated Patient

How does peak end-expiratory pressure (PEEP) assist a ventilated patient?

A) It provides positive pressure on expiration to keep small airways open.
B) It provides positive pressure on inspiration and expiration to increase oxygenation.
C) It delivers a breath in a set pattern regardless of the patient's respiratory pattern.
D) It delivers a breath only if the patient does not breathe spontaneously.