There are just two ways a moon could have been formed from the planet around which it travels: either part of the planet' s outer shell spun off into orbit around the planet or else a large object such as a comet or meteoroid, struck the planet so violently that it dislodged a mass of material from inside the planet. Earth' s moon consists primarily of materials different from those of the Earth' s outer shell. If the statements above are true, which one of the following, if also true, would most help to justify drawing the conclusion that Earth's moon was not formed from a piece of the Earth? ["Earth's moon consists primarily of elements that differ from those inside the Earth.", 'Comets and large meteoroids normally move at very high speeds.', "The craters on the surface of Earth's moon show that it has been struck by many thousands of large meteoroids.", "The moons of some planets in Earth's solar system were not formed primarily from the planets' outer shells."]