What must be done to the <canvas> element if it is used to present an image?

The correct choice emphasizes the importance of providing semantic information for assistive technologies when using the <canvas> element to present an image. Assigning the ARIA role="img" to the <canvas> element conveys to screen readers and other assistive devices that the content is an image. This is crucial because the <canvas> element itself does not inherently contain any descriptive text or semantic meaning about its content, making it vital to communicate its purpose and function explicitly.

By applying ARIA roles appropriately, developers ensure that users with disabilities can understand what the canvas represents, enhancing the overall accessibility of web content. This is especially important when the visual representation is key to understanding the information being conveyed, such as in charts, graphs, or complex illustrations that cannot be expressed with text alone.