When granite rocks undergo metamorphosis, they transform into different types of rocks. Option 1, Quartzite, is incorrect as quartzite is formed from sandstone, not granite. Option 3, Marble, is also incorrect as marble is formed from limestone. Option 4, Slate, is not the correct answer either as slate is derived from shale. The correct answer is option 2, Gneiss. Gneiss is a foliated metamorphic rock that is formed from the recrystallization of granite. During metamorphism, the minerals in the granite are realigned and rearranged, resulting in the formation of gneiss. This process can occur due to various factors such as high pressure, high temperature, or the presence of fluids. Gneiss is characterized by its banded appearance and can exhibit a wide range of colors and textures.