Read the poem "Nothing Gold Can Stay," by Robert Frost.

Nothing Gold Can Stay

Nature's first green is gold,

Her hardest hue to hold.

Her early leaf's a flower;

But only so an hour.

Then leaf subsides to leaf.

So Eden sank to grief,

So dawn goes down to day.

Nothing gold can stay.

Which line of the poem expresses the theme that youth passes quickly?

A. Nature's first green is gold

B. But only so an hour

C. Then leaf subsides to leaf

D. So Eden sank to grief