Which of the following describes a key feature of blocks in design?

The characteristic that highlights the significance of blocks in design is their ability to promote reusability and maintainability. Blocks are modular components that encapsulate a specific piece of functionality or user interface. By creating blocks, developers can use the same block across multiple screens or applications, minimizing redundancy. This not only saves development time but also enhances maintainability since any changes made to the block will automatically reflect wherever it is used. As a result, it fosters a cleaner codebase and a more organized project structure, aligning with best practices in software development.

In contrast, other statements present limitations that do not accurately represent the nature of blocks. The idea that blocks can only be placed in screens is inaccurate because they can also be used in other components, such as web or mobile apps, providing further flexibility. The notion that blocks are immutable once created doesn't correspond with their design purpose, as developers can modify them after creation as needed. Finally, stating that blocks can only contain one widget underestimates their potential; a block can comprise multiple widgets, allowing for complex functionality within a single modular component.