Potential effects of oxygen-deficient atmospheres (15-19% by volume) include:

The correct answer highlights that in an oxygen-deficient atmosphere, where oxygen levels are between 15% and 19% by volume, individuals experience a decreased ability to work strenuously. This condition occurs because the body requires a certain level of oxygen to perform physical activities effectively. When oxygen is scarce, the body’s ability to transport and utilize oxygen decreases, leading to fatigue, confusion, and impaired cognitive and physical performance.

Under normal atmospheric conditions, a person utilizes the available oxygen to maintain energy levels and sustain physical activity. However, when the oxygen concentration drops below the standard 20.9% found in ambient air, it can lead to symptoms such as shortness of breath, poor endurance, and a general decline in physical capacity. This directly impacts strenuous work capabilities, making it difficult for individuals to perform tasks that require significant exertion. Thus, a decrease in the ability to work strenuously is a logical and expected outcome in such environments.