This is a question with answer options. What kind of thing would the answer to the question "What does NN O `` mean when used as a prefix in Irish surnames ?" be an entity, an abbreviation, a description, a human, a location, or a numeric value?

Available options:
 A). description.
 B). entity.
 C). abbreviation.
 D). human.
 E). numeric.
 F). location.
C).