A Girl Walks on a Level Floor in a Straight

Multiple Choice

A girl walks on a level floor in a straight line in the +x direction.Her foot exerts a force on the floor.The direction of the reaction force by the floor on her foot is in

A) +x direction
B) -x direction
C) +y direction (vertically up)
D) -y direction (vertically down)
E) depends how fast she is walking