Answer: D)"If the fountain gushed at my very doorstep, I would not stoop to bathe my lips in it; no, though its delirium were for years instead of moments."
The most likely answer would be D. Dr. Heidegger is talking about the "water of youth" (or fountain of youth) and he explains that even if the fountain were right at his doorstep, he would not drink from it. This shows enormous will-power and strength. Therefore, these lines are the ones that better represent wisdom and reason.