Final answer:
The metamorphic process associated with differential stress is b) regional metamorphism, which occurs during large-scale tectonic events and often results in foliated rock textures.
Step-by-step explanation:
The metamorphic process most likely associated with differential stress is regional metamorphism (b). This process is typically involved in large-scale structural events such as tectonic plate collisions and the resulting deformation, which produces a high degree of foliation and mineral alignment due to the pressure exerted from multiple directions. Regional metamorphism occurs over vast areas and is most commonly found in mountain belts or ancient mountainous regions, where pressures and temperatures vary greatly and are often accompanied by large-scale folding and faulting.