Naturalism extends the concepts behind realism in that it

a. tries to imitate reality in a believable way.

b. creates real situations in a natural setting.

c. attempts to explain experiences without idealism.

d. explores the factors that motivate characters.

The answer would be : D. Explores the factors that motivate characters

If we're talking about Naturalism in the art and literature context, the style, character, and theory in the literature will be the representation based on accurate description and details. So in character, it's not only tell about what the character is doing, but it also tell about why he do it to create a more realistic feeling towards the reader