Answer:
I believe the best answer to be letter D. evil person.
Step-by-step explanation:
Logically speaking, if the characters in a story are people - not animals or objects - and we have a character versus character conflict, then both the protagonist and the antagonist will be a person. We can eliminate options A and C already. Now, we need to keep in mind that the protagonist is, in a very high percentage, a good person, or even a hero. He/she may not be perfect, but he/she has enough qualities to keep the audience on his/her side, hoping for his/her success. The antagonist, on the other hand, may not be entirely a bad person, but he/she becomes evil to the eyes of audience because his/her purpose is to defeat the protagonist somehow. The antagonist is the obstacle preventing the protagonist of achieving success. Especially when the protagonist is a hero, the antagonist is the evil force that tries to conquer the world, or kill the hero's loved ones. But even if his/her actions are not that extreme, the antagonist ends up being an evil person simply because he/she is the protagonist's enemy.