Question

planetary scientists have long relied on the giant impact hypothesis to explain the moons formation: a mars - sized body, theia, struck the proto - earth, creating a debris disk from which the moon coalesced. however, this model struggles to account for the nearly identical potassium isotope ratios found in earth and lunar rocks, as theia likely had a distinct chemical signature. to resolve this chemical puzzle, researchers simon lock and sarah stewart proposed a new object: asynestia, a rapidly spinning, doughnut - shaped mass of vaporized rock. in their model, the high - energy impact vaporized the impactor and the proto - earth entirely, allowing their materials to mix thoroughly in the synestia before the moon condensed from the vapor, thereby inheriting earths isotopic fingerprint.
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which choice best describes the function of the underlined sentence in the text as a whole?
a it introduces a theoretical concept designed to invalidate the empirical finding that challenged the prevailing view in the previous sentence.
b it presents a model that two researchers developed to account for the chemical similarity noted earlier in the passage.
c it describes the specific methodology used to detect the chemical similarities mentioned in the previous sentence.
d it summarizes the consensus view that existed prior to the discovery of the evidence mentioned in the first sentence.

Explanation:

1. Analyze the underlined sentence: "To resolve this chemical puzzle, researchers Simon Lock and Sarah Stewart proposed a new object: a 'synestia,' a rapidly spinning, doughnut - shaped mass of vaporized rock."

• The "chemical puzzle" refers to the nearly identical potassium isotope ratios in Earth and lunar rocks that the Giant Impact Hypothesis struggled to account for (the chemical similarity noted earlier).
• The sentence presents the new model (synestia) developed by the two researchers to account for this chemical similarity.

1. Analyze Option A: The underlined sentence is not designed to invalidate an empirical finding. It is to propose a solution to a puzzle, so A is incorrect.
2. Analyze Option C: The underlined sentence does not describe a methodology for detecting chemical similarities. It proposes a new model, so C is incorrect.
3. Analyze Option D: The underlined sentence is not a summary of a consensus view. It is a new model proposed by two researchers, so D is incorrect.

Answer:

B. It presents a model that two researchers developed to account for the chemical similarity noted earlier in the passage.