Hypoxia susceptibility due to inhalation of carbon monoxide increases as:

The correct answer is related to the fact that as altitude increases, the partial pressure of oxygen decreases. This reduction in oxygen availability can heighten susceptibility to hypoxia, especially when inhaling carbon monoxide, which binds to hemoglobin more readily than oxygen does. At higher altitudes, the body already experiences a decrease in available oxygen, which can exacerbate the effects of carbon monoxide exposure.

Inhalation of carbon monoxide prevents the blood from carrying sufficient oxygen to the tissues, and at altitude, where oxygen levels are low, the effects of carbon monoxide become more pronounced. Consequently, the vulnerability to hypoxia increases significantly in these conditions, highlighting the importance of understanding how altitude affects both oxygen supply and the impact of toxic gases like carbon monoxide.