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:
Kelsey's hand is pushing on a door.
According to Newton's third law, what other force must be happening?
A. The door is pulling on Kelsey's hand.
B. The door is pushing on Kelsey's hand.
Determine the correct option from the provided choices and reply with its corresponding letter.

B