what is the of the poem?

"Nature's first green is gold,
Her hardest hue to hold,
Her early leaf's a flower;
Bit only so an hour.
Then leaf subsidrs to leaf,
So Eden sank to grief,
So dawn goes down to day
Nothing gold can stay".

A. Nature and Beauty
B. Innocence cannot last.
C. Nature and Man
D. Sunset and sunrises are beautiful​