The best option about what the Duke reveals about himself as he speaks in "My last Duchess" is D) that he is a calculating villain.
Is this excerpt he is talking about how his first wife was pleased by anything and how his name was valuable and she did not pay enough tribute to the value of it, to a point where he might have ordered her killing.
"Oh, sir, she smiled, no doubt,
Whene’er I passed her; but who passed without
Much the same smile? This grew; I gave commands;
Then all smiles stopped together."
