To identify which sentence most strongly supports the correct answer to Question 5, we should look for a statement that encapsulates key themes related to existence, ecstasy, and the relationship between life and forgetfulness.
In this context, choice D: "And such is the paradox of living, this ecstasy comes when one is most alive, and it comes as a complete forgetfulness that one is alive,” stands out as it directly discusses the relationship between ecstasy and the experience of living, aligning closely with the theme of duality in existence.
Therefore, the answer is D.