What is the primary requirement for keyboard navigation in a user interface?

• A. All interactive elements must be reachable via keyboard.
• B. Keyboard navigation is optional.
• C. Only visible elements require keyboard access.
• D. Mouse events are enough.

Answer: (A)

The key idea is that every interactive element in a user interface must be reachable and operable using the keyboard. This means a user should be able to navigate to links, buttons, form fields, menus, and other controls using keyboard input (typically by tabbing through elements) and activate them without using a mouse. Providing a clear focus indicator helps users see where the keyboard focus is, and the focus order should be logical and predictable.

This is essential because many users rely on keyboards or assistive technologies, so making all interactive controls keyboard-accessible ensures the interface is usable by everyone. If an element that performs a function can’t be reached by keyboard, it effectively becomes inaccessible.

Ruling out the other options: keyboard navigation isn’t optional—you design for keyboard access to accommodate users who can’t or don’t want to use a mouse. Relying only on visible elements isn’t the criterion; visibility isn’t what guarantees accessibility. And mouse events alone aren’t enough because they exclude keyboard-only users and many assistive technologies.