The answer is not B. hoplites because those are heavy infantry in ancient Greece used but lots of city states not just by Sparta so the correct term is Helots and here is the definition-- a member of a class of serfs in ancient Sparta, intermediate in status between slaves and citizens.
Answer:
By undermining the authorities of the European authorities.
They wanted to present them as if they were gods. This was quite common in history and is a reason for example why pharaohs got pyramids built in their honor. The giant heads depicted their leaders as gods or someone who is in general larger than life itself. It was a sign of respect and others who would visit would also see this and know who they are dealing with. Such heads can still be found and examined which is important when trying to understand their ancient culture.