Final answer:
Metabolic acidosis in association with hypoxia is usually caused by impaired cellular respiration, leading to an accumulation of lactic acid and a decrease in blood pH.
Step-by-step explanation:
The factor that usually causes metabolic acidosis to develop in association with hypoxia is Impaired Cellular Respiration (Anaerobic Metabolism). When oxygen delivery to tissues is inadequate, cells are forced to produce energy through anaerobic pathways, leading to the production of lactic acid. The accumulation of lactic acid and other organic acids in the bloodstream causes the pH to fall, leading to metabolic acidosis. Conditions such as diabetic ketoacidosis, severe diarrhea, and renal dysfunction can also exacerbate metabolic acidosis by increasing acid metabolites or decreasing bicarbonate levels.