To determine the shape of the cross-section made by a slice parallel to the base of a right rectangular pyramid with four equal edges, we need to consider the properties of the pyramid.
In a right rectangular pyramid, the base is a rectangle (in this case, since it has "four equal edges," we can presume it might actually mean a square base). When a plane cuts parallel to the base of the pyramid, the resulting cross-section will be similar to the base of the pyramid, maintaining the same shape as the base.
If the base is a square (which is suggested by having equal edges), the cross-section will also be a square. If the base were a rectangle, the cross-section could still represent a rectangle but in a smaller size.
Therefore, the correct response would be:
square