A book rests on a table, which in turn rests on the floor. The floor exerts a force P on the table. Force P and one other force constitute a Newton’s Third Law interaction pair of forces. What is the other force?

Answer:

23) F

Newton’s Third Law:
If a body A exerts a force on body B, then B will exert an equal and opposite force on A.

The information given to us says that the floor (body A) exerts a force on the table (B). So the table must also exert an equal and opposite force on the floor.