They are all correct but A. Explains it the best
This is the statement that <span>best describes how Williams’s experiences with Native Americans differed from that of his contemporaries:
</span><span>Williams described the natives as very human, while other settlers described them as savage.
Obviously, their opinions differed greatly, insofar as Williams saw them as people they were, and the others could only see their animalistic side.</span>
Prepositions ususally stand before nouns, in this case "on" is the preposition.
