Unbalanced forces are acting on an object when the net force acting on it is not zero, meaning there is a greater force acting in one direction than in the other.
In the options provided, the situation in which unbalanced forces are acting on the tire 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 case, the forces are not directly opposing each other since they are acting in different directions (one pushing and one pulling), which results in an unbalanced force on the tire.