What aspect does visual design primarily emphasize?

Visual design primarily emphasizes aesthetics and presentation, which are crucial for creating an appealing interface that enhances user engagement. This aspect of design focuses on the visual elements such as color, typography, imagery, and layout to make the product not only visually attractive but also effective in communicating the brand and message. A good visual design can influence user perception and direction, guiding them through the interface intuitively.

In contrast, functionality pertains more to how well the product performs its intended tasks, which does not focus solely on the visual appeal. Usability testing results are critical for understanding how users interact with the product and ensuring a positive user experience, but they do not directly concern the visual aesthetic. Content management strategies are related to organizing and maintaining information within the system, which is separate from the visual presentation and design elements. Thus, the emphasis on aesthetics and presentation is what makes option C the correct choice.