Correct answer is 'D'.
A and C are completely out of context so we can first eliminate those. Confusion is b/w B and D.
The given paragraph no where talked about the true intentions of, why the great Ashoka left copious evidences in the form of stone carved edicts. So we can't consider ourselves like He did it so that he can be remembered. So option B is out.
It's clearly mentioned that historians predict the greatness of a king by the availability of evidences of his time. It also says Ashoka left behind stone carved edicts and today, we consider Ashoka as a great ruler. So in that way D is the correct answer.
PS :- key point for such kind of questions is, do not just suppose anything. Just like good listener, be here good reader and apply common sense without making any assumption.