You Are Standing in a Moving Bus, Facing Forward, and You

Multiple Choice

You are standing in a moving bus, facing forward, and you suddenly move forward as the bus comes to an immediate stop. What force caused you to move forward?

A) force of gravity
B) normal force due to your contact with the floor of the bus
C) force due to static friction between you and the floor of the bus
D) force due to kinetic friction between you and the floor of the bus
E) no forces were responsible for your fall.