A couple consists of two equal, parallel, opposite forces separated by a perpendicular distance, producing torque without net force. Steps: - Define a couple as two forces of equal magnitude F that are parallel, opposite in direction, and offset to create rotation on the rod. - Examine each diagram for force directions, magnitudes, and lines of action. - Verify if the forces result in zero net force (equal and opposite) and non-zero torque (separated lines). - Select the diagram where forces act at rod ends, perpendicular to the rod, in opposite directions. Why D is correct: - Diagram D shows two forces of magnitude F acting parallel but oppositely at opposite ends of the rod, perpendicular to its length, satisfying the couple definition for pure rotation (torque = F × d, net force = 0). Why the others are wrong: - A: Forces act in the same direction, producing net translation, not a couple. - B: Forces are not parallel, resulting in combined translation and rotation. - C: Forces act along the rod's axis, creating compression or tension, not a …