Which condition is likely to result from an oxygen-deficient atmosphere between 4-6% by volume?

An atmosphere that contains between 4-6% oxygen by volume is considered oxygen-deficient and can lead to significant physiological effects. In such conditions, the body is unable to receive enough oxygen to sustain normal functions, which can result in severe health consequences including loss of consciousness.

When individuals are exposed to an oxygen concentration in this range, they might not be able to maintain adequate brain function, leading to coma and convulsions. These symptoms occur because the brain and other vital organs are highly sensitive to oxygen levels. Without sufficient oxygen, brain activity can become disrupted, resulting in a state of unresponsiveness or convulsive episodes as the body attempts to cope with hypoxia.

In contrast, the other conditions listed, such as severe cognitive impairment, high blood pressure, and extreme agitation, may not directly arise from the specific oxygen deficiency represented in the question's parameters. While various oxygen levels can cause different effects, at 4-6% oxygen concentration, the most critical and immediate concerns are related to severe impairment of consciousness and convulsive reactions, confirming that coma and convulsions are the likely direct outcomes of this level of oxygen deprivation.