Context: Isaac Newton was born in the 1600s and studied how objects move. He discovered three fundamental laws about forces and motion. According to Newton's third law, for every force, there is an equal and opposite force.
Consider the following force:
Robert is pulling on a full suitcase.
According to Newton's third law, what other force must be happening?
A. The suitcase is pushing on Robert.
B. The suitcase is pulling on Robert.
Answer with the option's letter from the given choices directly.

B