Why does the speaker in "spring and fall" tell margaret that the source of her sorrow is "the blight man was born for"?

a.
he is suggesting that, even though she cannot yet express it, margaret intuitively recognizes the mortality of all human beings.

b.
he is referring, in veiled and symbolic terms, to an illness from which margaret suffers.

c.
he is explaining, in scientific language, why certain trees lose their leaves in the fall.

d.
he is asserting, as kindly as he possibly can, that margaret is being overly sensitive and immature over an unremarkable natural phenomena.

(if you answer the question, give me an explanation if applicable! i'm here to learn, not just get answers! )