Final answer:
The correct option is D. The partial pressure of oxygen at the venule end of pulmonary capillary beds should be approximately 100 mmHg, reflecting the efficient gas exchange and oxygenation of blood in the lungs.
Step-by-step explanation:
If the partial pressure of oxygen within alveolar tissues is 100 mmHg, the partial pressure of oxygen at the venule end of pulmonary capillary beds should be approximately the same due to the efficient gas exchange in the lungs. This process is facilitated by a strong pressure gradient that drives the diffusion of oxygen from the alveoli to the blood in the capillaries. Oxygen diffuses down its pressure gradient from an area of higher pressure in the alveoli to an area of lower pressure in the capillaries. As the blood passes through the pulmonary capillaries, it becomes oxygenated, and the partial pressure of oxygen in the venous blood approaches that of the alveoli.
In normal physiological conditions, when ventilation is optimal, the partial pressure of oxygen in the pulmonary veins is about 100 mmHg. This indicates that the correct answer to the student's question would be option D, 100 mmHg. This level of oxygen partial pressure reflects the efficiency of gas exchange across the respiratory membrane, where oxygen binds to hemoglobin in red blood cells and is then transported throughout the body.