What is the primary danger of diving with carbon monoxide in the gas mixture?

Diving with carbon monoxide in the gas mixture primarily causes hypoxia, which is a condition characterized by insufficient oxygen reaching the tissues. Carbon monoxide interferes with the blood's ability to carry oxygen by binding to hemoglobin more effectively than oxygen does, forming carboxyhemoglobin. This reduces the amount of oxygen available for essential bodily functions, leading to symptoms such as dizziness, confusion, unconsciousness, or even death if levels are high enough.

While other options present potential risks associated with carbon monoxide exposure, they do not directly address the most critical and immediate threat posed during diving: the loss of oxygen supply to vital organs. Hypoxia's effect can escalate quickly in underwater environments, making it crucial for divers to avoid any gas mixtures that could contain carbon monoxide.