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

Multiple Choice

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

A) the force due to friction between you and the floor of the bus
B) the normal force due to your contact with the floor of the bus
C) gravity
D) There is not a force causing you to slide forward.