A is a solid consisting of a square, a point not in the same plane as the square, and all points between them.
It can't be these
Triangle means the plane of the figure that is formed by connecting 3 particular points but it is not in a straight line. ←
Cube means the solid figure of having 6 square plane faces which that the angle between about 2 adjacent sides that is a right angle ←
SquarePrism means the shape of a square that has approximately 3 dimensional shape that has a rectangular sides and shape, but it has about 2 that are square ←