The correct answer is (A) An opponent, which one cannot overcome; that which a person cannot achieve or conquer; a rival whom one cannot beat. Also, punishment, retribution, or retributive justice, particularly for evil doing on an enormous scale.

Nemesis is the name of the Greek goddess of vengeance, the goddess of divine retribution.

Examples of use:

• The opening night reviews proved to be the director's nemeses.
• The university entrance examination became the student's nemesis.