To analyze the problem, we need to clarify the properties of the given right rectangular pyramid with four equal edges. This description suggests that the base is a square, and the edges of the sides (the slant edges) are equal in length.
If we make a slice parallel to the base of a right rectangular pyramid, the resulting cross section will be similar in shape to the base of the pyramid. In this case, since the base of the pyramid is square, the cross section will also be a square.
Therefore, the correct answer is:
B) Square