Correct Response: B. The prevailing hypothesis of the Moon's formation is that a protoplanetary body the size of Mars collided with Earth approximately 4.5 billion years ago, ejecting debris into Earth's orbit that coalesced into the Moon. Such collisions are thought to have been relatively common in the early solar system and this hypothesis is well-supported by the available evidence. The planetary-capture model (A) and the idea that a massive meteor was pulled in by Earth's gravitational field (C) do not appear to be physically likely as the velocity and mass of any such object would be too great to be captured by Earth's gravitational field. While the satellites nearest to the gas giants Jupiter and Saturn are thought to have formed from circumplanetary clouds of gas and dust (D), lunar evidence and Earth's composition suggest this was not how the Moon formed.
