Which person would be expected to have the largest A-a gradient?

Question

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[IV D]. Increased A-a gradient signifies lack of $\mathrm{O}_{2}$ equilibration between alveolar gas 
(A) and systemic arterial blood 
(A). In pulmonary fibrosis, there is thickening of the alveolar/pulmonary capillary barrier and increased diffusion distance for $\mathrm{O}_{2}$, which results in lack of equilibration of $\mathrm{O}_{2}$, hypoxemia, and increased $\mathrm{A}-\mathrm{a}$ gradient. Hypoventilation and ascent to 12,000 feet also cause hypoxemia, because systemic arterial blood is equilibrated with a lower alveolar $\mathrm{PO}_{2}$ (normal A-a gradient). Persons breathing $50 \%$ or $100 \% \mathrm{O}_{2}$ will have elevated alveolar $\mathrm{Po}_{2}$, and their arterial $\mathrm{PO}_{2}$ will equilibrate with this higher value (normal A-a gradient).

Which Person Would Be Expected to Have the Largest A-A 50%50 \%50%

Which Person Would Be Expected to Have the Largest A-A $50 \%$