Final answer:
The amount of oxygen that diffuses into the blood is determined by the functional surface area of the respiratory membrane, alveolar ventilation, and the oxygen pressure gradient.
Step-by-step explanation:
The amount of oxygen that diffuses into the blood each minute is determined by all of the above options mentioned in the question: the total functional surface area of the respiratory membrane, alveolar ventilation, and the oxygen pressure gradient between alveolar air and incoming pulmonary blood.
The respiratory membrane's large surface area allows for efficient gas exchange between the alveoli and capillaries. Alveolar ventilation ensures an adequate supply of oxygen in the alveoli. The oxygen pressure gradient drives the diffusion of oxygen into the blood.