Which of the following options is correct regarding the instantiation of Blocks in OutSystems apps?

The correct assertion is that Blocks can be instantiated on Screens and other Blocks. In OutSystems, Blocks serve as reusable components that help in building modular applications. This feature allows developers to create a Block that encapsulates a specific piece of functionality or UI and then utilize it across different Screens or even within other Blocks.

By enabling instantiation in other Blocks, OutSystems promotes a more organized and efficient coding structure, facilitating code reuse and reducing redundancy. Consequently, developers can create complex interfaces using small, manageable components, which boosts maintainability and scalability.

The other options limit the usage of Blocks in ways that do not reflect their full capabilities within the OutSystems framework. For instance, stating that Blocks can only be instantiated on Screens dismisses the flexibility and modular nature that is essential for effective application development. Similarly, the assertion that Blocks can only be instantiated on Client Actions or external HTML pages does not accurately represent the intended use of Blocks within the OutSystems environment.