The correct answer is "Zero".
A couple is a pair of equal and opposite forces that are separated by a certain distance. The forces produce a rotational effect on an object, but do not produce any linear motion. The resultant force of a couple is always zero because the two forces are equal and opposite. This means that they cancel each other out, and there is no net force acting on the object. The rotational effect of a couple is known as torque, which is a measure of the twisting force that causes an object to rotate.