Concept:Gneiss is a high-grade metamorphic rock whose original rock type is granite.
Explanation:Metamorphic rocks form when existing rocks are changed by heat and pressure.
This process is called metamorphism, meaning “change in form.”
The original rock is known as the protolith.
For gneiss, the protolith is granite.
Under intense temperature and pressure, granite recrystallizes to form gneiss.
This produces typical banded layers in gneiss.
Therefore, gneiss is not formed from slate, shale, or sandstone.
Answer:A. Granite