Which keyboard shortcut can be used to restart an application on Windows?

The chosen answer is correct because the keyboard shortcut ALT+F4 is commonly used in Windows to close the currently active application. However, after closing the program, you can subsequently relaunch it immediately after using ALT+F4, effectively restarting it. This shortcut can be useful in scenarios where an application is unresponsive; closing the program through this shortcut allows the user to quickly restart it without navigating through menus.

The other options serve different purposes: CTRL+R typically refreshes a webpage or document in many applications, ALT+TAB is used for switching between open applications rather than restarting them, and CTRL+S is a command for saving work in progress. Each of these options has its respective function, but they do not facilitate the process of restarting an application as effectively as ALT+F4 does in conjunction with relaunching the application.