Concept:A couple is formed by two equal, parallel and opposite forces.Their vector sum cancels out, so the resultant force is zero.Explanation::Consider two forces of equal magnitude F acting in opposite directions.Their vector sum is written as:Fresultant=F+(−F)=0Therefore, the net force on the body is zero.However, the couple still creates a nonzero turning moment or torque.This moment depends on the perpendicular distance between the two forces.Hence, the resultant force of a couple is always zero, not the sum or product of the forces.Answer:A. zero