What the theme?

Read the excerpt from "Ozymandias."

And on the pedestal these words appear:
"My name is Ozymandias, king of kings;
Look on my works, ye Mighty, and despair!”
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

Which theme does this excerpt best support?

A. No power lasts forever.
B. Absolute power corrupts.
C. Being powerful is all that matters.
D. Having power is the greatest gift.

im pretty sure its a or b?