What is the web accessibility standard that ensures usability for people with disabilities?

WCAG, or Web Content Accessibility Guidelines, is the correct choice because it provides a comprehensive set of guidelines designed specifically to make web content more accessible to individuals with various disabilities. These guidelines outline how to create accessible web applications and content, focusing on aspects such as text alternatives for non-text content, adaptable layouts, and ensuring that the content is perceivable, operable, understandable, and robust across a wide range of devices and technologies.

By adhering to WCAG standards, developers can significantly improve the usability of websites for people with disabilities, ensuring equitable access to information and functionalities. The guidelines are developed by the World Wide Web Consortium (W3C) and are a fundamental part of promoting an inclusive web experience.

In contrast, HTML5 is a markup language used for structuring web content but does not inherently provide accessibility features. W3C standards encompass a broader range of web technologies and best practices, while ARIA is a set of attributes that enhance HTML to improve accessibility but does not serve as a standalone framework for web accessibility like WCAG does.