There is no such thing as "an unbalanced force".
The group of all forces acting on an object is either balanced or unbalanced.
-- If the forces acting on an object are unbalanced, then the object is accelerating ... its speed or direction is changing.
-- If the forces acting on an object are balanced, then the object is not accelerating ... its speed and direction are not changing.
-- If neither the speed nor the direction of an object is changing, then the forces on the object are balanced.
-- If either the speed or the direction of an object is changing, then the forces on the object are unbalanced.
-- Neither the speed nor the direction of a book on the shelf, a paper on the floor, or a glass on the table are changing. The forces on these objects are balanced. (A, B, and C)
-- The speed of a model rocket is changing. The forces on the model rocket are unbalanced. (D)