By definition, a solid is a three dimensional object.
A net is defined as a shape of two dimensions that forms a solid when it is folded.
In this case you know that the net mentioned in the exercise has six squares. These squares are the faces of the solid.
By definition, a cube is a three dimensional object that has six square faces, eight vertices and twelve edges. All its faces are equal.
Based on the explained above, you can conclude that a cube could be made from a net that has six squares.
The answer is: A cube.