I’m obliged to make a Hitchhiker’s Guide reference and say that (D) is the best answer, because, you know, Magratheans,
In all seriousness, the student’s answer is not correct either. Yes, you could argue that without the Big Bang, the raw materials from which Earth was formed would not exist, but you could make that argument about anything. Teletubbies were created by the Big Bang. Kevin Bacon was created by the Big Bang. Pepsi and Coca-Cola were both created by the Big Bang.
Besides, there were nine billion years (give or take) between the beginning of the Big Bang and the formation of Earth. For nearly two-thirds of the Universe’s history, there was no Earth.
The Big Bang is horribly misnamed. The name gives the impression that matter and energy exploded into pre-existing space. That’s not accurate at all. The current Big Bang model holds that space itself expanded from an infinitesimal point of unimaginable density and temperature. The nascent Universe expanded and cooled rapidly, but even so it was more than 370,000 years before the Universe was cool enough to allow simple atoms to form. At that early stage, the only elements available were hydrogen and helium – the two lightest elements. The ingredients needed to make Earth – silicon, oxygen, iron, nickel, and so on – were virtually absent and would be for many millions of years. Bottom line: Earth did not spring fully formed from the wake of the Big Bang. From whence cometh Earth then?
The first stars lit up about 200 million years after the Big Bang started. In their cores they fused hydrogen, and eventually helium, into heavier elements. When the most massive of these stars ended their lives in supernova explosions, they scattered the periodic table across the cosmos. With each star’s death, the universe became richer in terms of elemental diversity. Subsequent generations of stars had planets – and not just hydrogen-rich gas giants like Jupiter, but rocky planets as well. Then a rocky planet happened to form at just the right distance from its parent star so that liquid water could exist on its surface, and 4.6 billion years later we’re all arguing about who started it all.
But we still haven’t answered this poor girl’s test question: who or what created Earth? I suppose you could say God if you’re religious, but that isn’t a scientific answer and this is clearly a science test. If I were going to write in an answer, it would be (E) gravity.
That’s it. Gravity caused Earth to condense from a cloud of gas and dust orbiting the Sun (which was also busy accumulating mass via the persistent tug of gravity). You can break it down and look at the nitty gritty details, but at the end of the day, it’s just gravity.
Sorry it’s not more awe-inspiring, but that’s life.