Final answer:
The correct rule to reflect a quadrilateral across the x-axis is (x, y) --> (x, -y), keeping the x-coordinates the same while reversing the sign of the y-coordinates.
Step-by-step explanation:
The reflection of a quadrilateral across the x-axis can be described by a transformation rule that flips the quadrilateral vertically but maintains its horizontal position. This means that the x-coordinates of the vertices remain unchanged, while the y-coordinates are multiplied by -1. For quadrilateral JKLM with vertices J(-6, 8), K(-3, 8), L(-5, 2), and M(-9, 5), the correct transformation rule that represents a reflection over the x-axis is (x, y) --> (x, -y).