Amy gets up from her seat on the train to move closer to the front of the train. Just as she begins to walk toward the front, the train stops at a station.

Which of Newton's laws explains what happened to Amy?

A.
While Amy was walking, her body was in motion, but as the train stopped, it exerted a force on Amy opposite to the direction she was walking and caused her to also stop. This is an application of Newton's Third Law of Motion.

B.
While Amy was walking, her body was in motion, but when the train stopped, she experienced an unbalanced force and continued to move forward due to inertia. This is an application of Newton's First Law of Motion.

C.
While Amy was walking, her body was in motion, but when the train stopped, an unbalanced force accelerated her body backward. This is an application of Newton's Second Law of Motion

D.
While Amy was walking, she was in motion due to the force of repulsion. When the train stopped, she was catapulted forward due to the train's stronger force of attraction. This is an application of Newton's Law of Universal Gravitation.