I believe it’s D, an applied force.
A reaction force seems to refer to Newton’s third law, but is relatively vague to be the answer to this question.
An expected force isn’t a concept nor the name of any subject of forces that is taught within the physics textbooks.
A positive force refers to direction, a negative force can have less, equal, or even more magnitude than the positive force, thus it contradicts itself. As that’s still a force that can push or pull.
So I believe it to be D.
