A total obstruction of the airway by aspirated material is manifested by:

A. Oxygen does play a role in maintaining acid-base balance indirectly, as it is required for aerobic metabolism, which produces carbon dioxide that is regulated by the body to maintain acid-base balance. However, this is not its primary role.

B. Oxygen does trigger chemoreceptors, but this is more of a secondary function to regulate breathing based on oxygen and carbon dioxide levels.

C. While oxygen has many roles, its most critical function is providing the necessary support for cellular metabolism, which is vital for energy production in cells.

D. Oxygen is essential for cellular metabolism as it is required for the process of oxidative phosphorylation in mitochondria, which produces ATP, the energy currency of cells.

A. Rectal filling is associated with the urge to defecate, not urinate. It is not involved in the micturition process.

B. Mass movements refer to strong, coordinated contractions of the colon, which help move feces toward the rectum. They are related to bowel movements, not micturition.

C. Micturition, or urination, is primarily stimulated by bladder filling. As the bladder fills with urine, stretch receptors in the bladder wall are activated, sending signals to the brain to trigger the urge to urinate.

D. Segmental movement refers to the mixing contractions in the intestines that aid digestion, not the process of micturition.