What version number must 'WCAG-VER' meet for EPUB publications?

The correct answer is based on the established guidelines for making EPUB publications accessible. The Web Content Accessibility Guidelines (WCAG) are vital in ensuring that digital content, including EPUB files, is usable by people with disabilities. To comply with the accessibility standards set forth for EPUB publications, the version of WCAG that must be adhered to is 2.0 or higher.

WCAG 2.0 introduced significant improvements and a more robust framework for ensuring web content is accessible, focusing on four main principles: Perceivable, Operable, Understandable, and Robust. By stipulating that EPUB publications must meet WCAG 2.0 or higher, it ensures that they are designed with accessibility in mind, thereby providing a better experience for users with varying abilities.

The options indicating earlier versions, such as 1.0 or 1.1, do not meet the current standards of accessibility required for modern digital publications. Therefore, they are not sufficient for ensuring compliance with contemporary accessibility needs. Additionally, while WCAG 3.0 does exist, as of now, it is not yet formally adopted as a standard for EPUB, making 2.0 the correct and relevant version to reference for publishers and developers in this context.