Answer :
The correct answer for this question is: "b. He never yet a boorish thing had said/ In all his life to any." The excerpt from "The Prologue" of The Canterbury Tales that best indicates that the Knight is a humble person is that he never yet a boorish thing had said in all his life to any. Being humble is showing modest or low estimate of own importance.
In the Knight's Tale, The Knight is depicted as distinguished, chivalrous, humble, wise, brave and he is respected by others. He has gone to many battles during Holy Wars. Exact demonstration of his character is given below with this excerpt:
"He was of sovereign value in all eyes. And though so much distinguished, he was wise And in his bearing modest as a maid. He never yet a boorish thing had said In all his life to any, come what might; He was a true, a perfect-gentle knight."