Final answer:
When a subsystem has a large number of unrelated objects, its cohesion is low. Cohesion represents how closely related elements within a subsystem are, with high cohesion being preferable for maintenance and clarity.
Step-by-step explanation:
When a subsystem has a large number of unrelated objects, then its cohesion is considered to be low. Cohesion is a measure of how closely related the elements within a module or a subsystem are. In software engineering, a subsystem with high cohesion would consist of elements that are closely related in function, thereby contributing to that subsystem's single, well-defined task. Conversely, if a subsystem contains many unrelated objects, the lack of relationships and interdependencies among these objects means that the subsystem would have many different and unrelated functions, which results in low cohesion.
High cohesion is generally preferable because it leads to systems that are easier to maintain, debug, and understand. A module or subsystem with low cohesion would most likely be more complex to maintain and understand, as it may be serving multiple purposes without a clear, unified objective.