Which combination is most useful for creating an effective focus in a monochromatic composition?

Correct answer: Contrast of value, size, texture, and edges

A monochromatic composition is based mainly on one hue, so hue change alone cannot provide enough separation. Emphasis must be created through other visual variables, such as light–dark value, relative size, surface texture, and sharp or soft edges. Using several cues together makes the focal area clear without breaking the monochromatic scheme. Equal values reduce distinction, while symmetry alone does not guarantee a focus. Therefore, option C is correct.