Which of the following provides two reasons why two different masses dropped from the same height in a vacuum reach the ground simultaneously?

a) There is no air resistance present in a vacuum, eliminating any differences in the effect of air resistance on the falling objects.

b) In a vacuum, there is no medium to exert buoyant force, ensuring equal acceleration due to gravity for both masses.

c) The absence of air in a vacuum means there is no difference in the gravitational force acting on each mass, leading to equal acceleration.

d) Without air, there are no external forces acting on the falling masses, allowing them to experience the same acceleration due to gravity.