Explanation
Correct answer: D.
Choice D is the best answer. The sentence describes how scientific understanding of the glass’s origin has evolved, explaining that new research suggests the glass formed as a result of a cometary explosion instead of being caused by grass fires (as was previously believed).
Why the other choices are wrong
Choice A
Choice A is incorrect. The sentence explains the conclusion of the older study; it doesn’t describe how scientific understanding of the glass’s origin has evolved.
Choice B
Choice B is incorrect. While the sentence indicates that the two studies provided different explanations, it doesn’t describe how scientific understanding of the glass’s origin has evolved.
Choice C
Choice C is incorrect. The sentence references a recent finding but doesn’t effectively describe how scientific understanding of the glass’s origin has evolved.