What can be used to provide various visual designs for pages in a WordPress site?

The correct choice is themes. In WordPress, themes are collections of templates and stylesheets that dictate the overall appearance and layout of a website. They allow users to change the visual design of their site by applying predefined styles and structures without the need for extensive coding knowledge. Each theme can offer different features, colors, fonts, and layouts, giving users the flexibility to customize their site's look to match their brand or personal preferences effectively.

While plugins, widgets, and templates each serve different purposes within the WordPress ecosystem, they do not primarily provide visual designs for pages. Plugins extend the functionality of a website, widgets are small blocks that provide specific content or features to a sidebar or footer, and templates serve as specific page layouts that are used within a theme rather than the overarching design. Thus, themes are specifically designed for visual design and aesthetics, making them the correct answer.