I believe the best answer for this question is D, "rhythm." Let us consider what each of these terms mean. "Focal emphasis" means the element that draws your attention the most. "Contrast" involves elements that are very different from each other, usually juxtaposed together to create an effect. "Rhythm" means repetition, arrangement, or flow. "Composition" means the way something is composed. Hope this helps.
This beautiful altarpiece is by the Italian Renaissance painter Carlo Crivelli. It represents the Madonna and Child enthroned with Saint Jerome and Saint Sebastian.
