Which of the following is a theory explaining near-death experiences?

Cerebral anoxia is a theory explaining near-death experiences by positing that these experiences may result from a lack of oxygen to the brain. When the brain is deprived of oxygen, it can lead to altered states of consciousness and vivid sensory experiences that individuals report during near-death situations. This theory suggests that the brain might generate these experiences as a form of survival response, leading to sensations such as bright lights, a feeling of detachment from the body, and other phenomena often described by those who have had near-death experiences.

The other options, while they relate to understanding aspects of near-death experiences, do not function as direct explanations in the same way. Existential philosophy explores life's meaning and human existence, which might frame a person's outlook on death but does not specifically explain the physiological aspects of near-death experiences. Life review phenomena describe the reflection or evaluation of one’s life that some people report during these experiences, but this is more of a reported phenomenon rather than a causal explanation. Mystical experiences, although they can accompany near-death experiences, refer broadly to spiritual or transcendent encounters that occur under various circumstances and do not exclusively account for the physiological reactions occurring in critical situations.