Final answer:
A design change in the process control block affects the degree of interdependence between OS modules, referred to as coupling, which is the correct answer to the question posed.
Step-by-step explanation:
A design change in the structure or semantics of the process control block (PCB) could have significant implications on the coherence and compatibility of different modules within the operating system (OS). The terms provided in the options refer to software design principles. Let us look at what each term means:
Coupling refers to the degree of interdependence between software modules. High coupling means modules are heavily reliant on each other, which makes maintenance and changes more difficult.
Abstraction is the concept of hiding the complex reality while exposing only the necessary parts.
Encapsulation is related to hiding the internal state of an object and requiring all interaction to be performed through an object's methods.
Cohesion refers to the degree to which elements of a module belong together. Higher cohesion within a module means that its functions are closely related to each other, improving maintainability and understanding.
A design change in the PCB affects how the OS interacts with its processes, and therefore could impact multiple modules due to a change in how they interconnect or communicate, which relates to coupling. Hence, the correct answer to this question is A) Coupling.