Granite is found in continental crust formed from contact metamorphism a chemical sedimentary rock an extrusive igneous rock

Granite is "an extrusive igneous rock." Igneous rocks are formed from the cooled lava that is flown after a volcanic eruption. When lava is cooled, it is turned to rock. Since the cooling take sometime, there are crystals that developed over time. This is the reason why you can big crystals to granite.

I'm pretty sure it's c. extremely gradual but not 100% sure though.

Answer (d) may increase or decrease porosity through dissolution or deposition;