What is called regional metamorphism?

Question

$\begin{array}{1 1} (a)\; \text{when temperature and pressure are applied together to form rock} \\ (b)\; \text{when temperature and heat are applied together to form rock } \\ (c)\; \text{when heat and pressure are applied together to form rock } \\ (d)\; \text{when water and pressure are applied together to form rock } \end{array}$