The cerebrum is the largest part of the brain, or answer A. This is the part of the brain that is most directly located behind the forehead. There are two hemispheres - a left and a right - that are separated by a sort of fissure of tissues.
This part of the brain is responsible for a lot of the voluntary activity in the brain. It basically helps you run, walk, jump, dance, etc. Anything that isn’t necessary for a functioning body (breathing and that kind of thing) is pretty much controlled here. It also helps with smells, languages, memories, and learning in general.
This is what schools are trying to engage when they teach you, but sometimes it doesn’t work out in the school’s favor.