Option D is correct, As partial pressure of oxygen in expired air is 116mm of Hg

Partial Pressure of Oxygen in Different Locations

1. Alveolar Air:
The alveolar air refers to the air present in the alveoli of the lungs, where gas exchange occurs. The partial pressure of oxygen in the alveolar air is relatively high due to the process of ventilation and perfusion. Ventilation ensures a fresh supply of oxygen-rich air reaches the alveoli, while perfusion allows blood to flow through the capillaries surrounding the alveoli. As a result, the partial pressure of oxygen in the alveolar air is high and reaches its maximum value.

2. Arterial Blood:
Arterial blood carries oxygenated blood from the lungs to the various tissues and organs of the body. After gas exchange in the alveoli, oxygen diffuses into the blood and binds to hemoglobin within red blood cells, forming oxyhemoglobin. The partial pressure of oxygen in arterial blood is high due to the efficient exchange of oxygen in the lungs and the transportation of oxygen-rich blood to the tissues.

3. Venous Blood:
Venous blood refers to the deoxygenated blood returning to the heart from the tissues. During its journey through the body, oxygen is delivered to the tissues, and carbon dioxide, a waste product, is produced. As a result, the partial pressure of oxygen in venous blood is relatively low compared to arterial blood. However, it is still higher than the partial pressure of oxygen in expired air.

4. Expired Air:
Expired air is the air that is exhaled from the lungs. It contains a higher concentration of carbon dioxide and a lower concentration of oxygen compared to alveolar air. When we breathe out, the partial pressure of oxygen in expired air is lower than that in alveolar air, arterial blood, and venous blood.

Conclusion:
Among the given options, the maximum partial pressure of oxygen is found in arterial blood. This is because arterial blood carries freshly oxygenated blood from the lungs to the tissues, ensuring a high partial pressure of oxygen. The partial pressure of oxygen is also high in alveolar air due to efficient gas exchange in the lungs, but arterial blood has the advantage of actively transporting oxygen to the tissues. Venous blood and expired air have lower partial pressures of oxygen compared to arterial blood.