Which option cannot be set as the On Click Destination for a Button in a Screen?

The correct answer is that a Block cannot be set as the On Click Destination for a Button in a Screen. In OutSystems, buttons are typically configured to perform actions when clicked. The On Click Destination is meant to define what happens as a result of that action, and while buttons can navigate to screens or external sites, or trigger client actions, they cannot navigate to a Block directly.

Blocks are reusable components that encapsulate UI and logic, but they don't serve as navigation targets. Instead, they are intended to be composed within screens or other blocks. They provide a way to structure the application and enhance modularity, but the on-click behavior of UI elements like buttons is limited to navigating to screens or triggering actions that can update the UI or perform calculations. Client Actions are designed to run scripts or server-side logic, while External Sites direct users to web addresses outside of the OutSystems application.

Understanding this distinction is key in designing intuitive user interfaces within OutSystems applications.