Need help please...what is the theme of this poem below.

Little drops of water,
Little grains of sand,
Make the mighty ocean
And the pleasant land.
Thus the little minutes,
Humble though they be,
Make the mighty ages
Of eternity.
-"Little Things" by Ebenezer Cobham Brewer

What is the theme of this poem?

a) Life is too complex to understand.
b) Patience helps us to survive the passage of time.
c) Nature is mighty and beautiful.
d) Each individual thing is important.