Answer:
C. Existing minerals become elongated and take on a foliation.
Explanation:
The process in which a metamorphic rock undergoes metamorphism into shale is called "schistosity". Schistosity can be described as a foliation process that can happen at medium or high levels of metamorphism. The important thing to remember about this process is that, during the metamorphism of the metamorphic rock, the minerals become tabular and elongated, assuming a medium granularity that makes them visible to the naked eye. these minerals line up in the same direction, allowing the rock to assume smooth or wavy planes on its surface.