The correct answer is dishonor.
The correct answer is (C) To dishonor; to tarnish or soil; to detract from (the honor, luster of; etc.); to dim the brightness of.
Besmirch comes from Latin be (completely) and English smirch (to stain).
Examples of use:
- The players' misdeeds besmirched the team's good reputation.
- The candidate besmirched his rival's honor.