Which phrase defines “protagonist” best?

a character or force that brings conflict
a character with positive qualities
a character or force that creates a more interesting story
a character, usually a main one

usually a main character

Explanation:

The answer is indeed letter D) A character, usually a main one.

Explanation:

The protagonist of a story is the central character, the lead figure around whom the story revolves. The events connected to this character and his/her actions and reactions determine the plot of the story. It is very common to associate good qualities to a protagonist, or to think of him/her as a hero. However, being the center of the plot does not mean the protagonist is good by nature. There is plenty of ambiguous protagonists, and even evil ones, in narratives, poems, movies etc. The climax of the story also depends on this character. After handling conflicts that build tension up, protagonists have to face a final challenge that usually produces a great change in their world or in themselves.

because they were not just any seashells they were sally's seashells