What does cohesion measure in module design?

Cohesion measures the degree to which the elements within a module belong together. A module with high cohesion means that its components are closely related and work together to fulfill a specific task or function, which enhances maintainability and understandability. High cohesion is desirable because it makes the module more self-contained and easier to manage, which helps in both development and future changes.

In module design, it's important for a module to focus on a single responsibility or a cohesive set of related responsibilities. This helps avoid confusion and makes it easier for developers to locate and fix issues, enabling better collaboration among team members.

The other options focus on different principles of software design. For instance, the degree of interdependence between modules relates to coupling, which is concerned with how dependent modules are on each other. The complexity of the system and the efficiency of data handling are broader system characteristics that do not specifically pertain to the measure of cohesive components within a single module.