Unbalanced forces are present when the total net force acting on an object is not zero. In the options provided, the situation that describes unbalanced forces is:
"Two people stand on the same side of a large tire. One person pushes the tire and the other pulls the tire with equal force."
In this scenario, even though the forces are equal in magnitude, they are acting in opposite directions (one push and one pull), creating an unbalanced force on the tire, which may cause it to move or accelerate in the direction of the resultant force.