What aspect of fiction did realist writers use to advance the plot of their story? a. the effect of destiny b. social trials c. tragic events d. complexity of character

I believe the correct answer is D. complexity of character.
A is incorrect because realist writers didn't believe in destiny; B is incorrect because not all realist novels have social trials; C is incorrect for the same reason - not all realist novels have tragic events. Therefore I would pick D, because complex characters reflect reality and what exists in our actual lives.