Which of the following describes hypoxia?

Hypoxia refers specifically to a deficiency of oxygen in the tissues, which can occur even if the blood oxygen levels appear normal. This condition can arise from various factors, including poor oxygen delivery, inadequate blood flow, or cellular inability to utilize oxygen effectively. While oxygen saturation and arterial blood gas levels can reflect overall oxygenation status, hypoxia emphasizes the impact on tissue oxygenation.

While other options mention oxygen levels in the blood or refer to carbon dioxide levels, they do not capture the essence of hypoxia. Oxygen levels in the blood can be normal while tissues may still be deprived of adequate oxygen. Thus, option C correctly identifies the critical aspect of hypoxia as it relates to cellular or tissue oxygen availability, which is essential for the proper functioning of metabolic processes.