Why are the following lines ironic?

"'My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!'"

a. Ozymandias never ruled anything.
b. The inscription was intended to "mock" the king that the statue portrays.
c. We know that shortly after the statue was erected, Ozymandias was killed in a battle with the Persian Empire.
d. All of the great works of the king have decayed to ruin.
e. none of these