Regarding Placeholders, which of the following options is correct?

A Placeholder serves as a designated area within an interface that will be filled dynamically when the block is instantiated. When you create a block with Placeholders, you're essentially outlining regions of the interface that can be populated with content later. This feature allows for greater flexibility and modularity in the design, enabling developers to create reusable components that can adapt based on the specific requirements of different scenarios.

In the context of other choices, it is not required to place at least one widget inside Placeholders upon instantiation; they can remain empty if necessary. Additionally, Placeholders can indeed be added to both screens and blocks, offering the same level of flexibility across different types of components. Finally, there is no restriction on having just one Placeholder in a block; multiple Placeholders can coexist within the same block, allowing for a variety of content placements. This flexibility is essential for building a dynamic user interface in OutSystems applications.