What is the theme of the poem “Spring and Fall” by Gerard Manley Hopkins?

Margaret, are you grieving
Over Goldengrove unleaving?
Leaves like the things of man, you
With your fresh thoughts care for, can you?
Ah! as the heart grows older
It will come to such sights colder
By and by, nor spare a sigh
Though worlds of wanwood leafmeal lie;
And yet you wíll weep and know why.
Now no matter, child, the name:
Sorrow’s spríngs are the same.
Nor mouth had, no nor mind, expressed
What heart heard of, ghost guessed:
It is the blight man was born for,
It is Margaret you mourn for.

A.
Nature outlasts man.
B.
Everything has a meaning.
C.
All things must pass away.
D.
Children are close to nature.