Which of the following best describes input devices?

Input devices are hardware components used to provide data and control signals to a computer system. They enable users to enter data into the system for processing. In this context, devices such as the mouse and keyboard are quintessential examples of input devices because they allow users to interact with the computer, execute commands, and input textual or graphical data directly.

The mouse facilitates point-and-click actions, providing a means for users to navigate through graphical user interfaces, while the keyboard serves as a tool for typing text and executing commands. Together, they are fundamental in everyday computer operations, supporting a broad range of applications.

Other options include devices that do not primarily serve the function of inputting data into a computer. Scanners and printers relate to input and output functionality but are not purely input devices. Monitors and projectors serve to output visual information, and speakers and headphones are involved in audio output, none of which provides data input to the system. This distinction highlights why the mouse and keyboard are appropriately categorized as input devices, while the other selections do not fit this definition.