Coupling refers to the degree of interdependence between software modules. A high amount of coupling indicates that the modules are highly dependent on each other, while low coupling indicates that they are more independent. Statement A describes a building block using an interface of another building block, which implies a form of interdependence or connection between the two blocks, indicating coupling. Statement D describes a building block using internal data structures of another building block, which also suggests a strong form of interdependence and direct access, indicating even tighter coupling. Cohesion, on the other hand, refers to how closely related and focused the responsibilities of a single module are, so statement C is not about coupling.