In a right rectangular pyramid with four equal edges, a slice made parallel to the base will create a cross-section that is similar in shape to the base of the pyramid. Since the base of the pyramid is a rectangle, slicing it parallel to that base will result in a smaller rectangle as the cross-section. However, because the question suggests that the pyramid has "four equal edges," it implies a specific configuration that might lead to additional considerations such as symmetries.
Given the information, the slice would most accurately correspond to a rectangle. However, it appears that rectangle is not among the options provided.
Among the options (trapezoid, hexagon, triangle, square), the best fit for a cross-section parallel to the base would be a trapezoid since rectangles can be viewed as special cases of trapezoids (specifically where the two bases are equal).
Thus, the correct response would be trapezoid.