What allows us to stand upright and keeps us from falling through the ground? a. while gravitational force pulls us down, the opposing force from the ground pushes up and balances out the two forces c. while gravitational force pulls us down, the ground is pulling us down too b. the force of gravity is stronger than the force of the ground pushing up on us d. the force of the ground pushing up on us is stronger than the force of gravity select the best answer from the choices provided a