Select the most appropriate option that can substitute the highlighted segment in the given sentence.
To the general public, William was best known as a crusader for peace and as an admired critic about social, political and ethical subjects.

Correct option is B

The correct substitution is (b) for peace and as an admired critic on.
Explanation: The correct preposition after "critic" when referring to the subject of criticism is "on."
The phrase "critic on social, political and ethical subjects" correctly conveys the idea.
Example: She is a renowned critic on modern art.