A

Step 1: Understand that when you are running and suddenly stop, your body experiences a change in motion.
Step 2: This change is due to the force acting opposite to your direction of motion.
Step 3: According to Newton's second law, the net force acting on an object is equal to the mass of the object multiplied by its acceleration (F = ma).
Step 4: In this case, the force that brings you to a stop is friction between your feet and the ground, which acts in the direction opposite to your motion, causing deceleration.
Therefore, the force responsible for your deceleration is friction.