The two will fall at the same speed and reach the surface at the same time. This is because the two will experience the same gravitational acceleration on the moon. However, on the earth surface the two will land on the surface of the earth at the same time due to air resistance such that the egg will experience a higher air resistance than the hammer. On, the moon, where there is no noticeable atmosphere there is no air resistance on either object and both fall at the same speed. It is also important to note that their mass doesn't affect their speed.
The answer is A.Refraction
One of the most famous historical model was the geocentric model thought of by plato. This model says that the earth is in the center of the universe and that each of the planets follow complicated paths that go backwards sometimes. This model was used until a new one was accepted. This model is the one we have today called the heliocentric model. It was bought of by Copernicus. Hope that answers your question!
