Answer:
D. What motivates the characters
Step-by-step explanation:
Characterization is a literary device that writers use to develop fictional characters in a story, that is to say, to reveal the readers a character's physical appearance, personality, interests, or motifs, whether indirectly or directly. Therefore, when authors reveal what motivates the characters in a story, he or she is using characterization.
The other options are incorrect because the information about where and the time period the characters live in is part of the information that is revealed through the setting, and the central conflict of the story is part of the plot itself.