To determine which sentence best develops the idea expressed in paragraph 2, we would need more context about what paragraph 2 actually discusses. However, a good response can be inferred based on what typically might be included in a paragraph discussing research findings.
Given the options provided:
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“By targeting more than 3,000 genes of interest, the researchers could tease out the variations between humans and tortoises." – This sentence focuses on the methodology of the research and sets the stage for the discoveries made.
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“Thanks to this analysis, the researchers were able to narrow down their original list of 3,000 genes to 43 specific sequences that might have contributed to Lonesome George’s long, disease-free life.” – This sentence would build on the findings and show the results of the analysis, likely connecting back to the idea of genetic factors contributing to longevity and health.
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“Their long, slow existence ‘has been key to their survival — from a time of overexploitation to a time of greater enlightenment and conservation,’ she wrote in an email.” – This referees more to the evolutionary perspective and conservation success.
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“Lonesome George was a conservation icon, Caccone said, but a conservation icon that can also provide insights into human health and aging.” – This sentence brings the discussion back to human relevance but may not directly relate to specific findings.
Assuming paragraph 2 discusses research findings related to genetic contributions to health or longevity, the second sentence seems to best support and develop the idea expressed in that paragraph, as it directly relates to the narrowing down of genes studied and connects to the long life of Lonesome George.
So, the best choice is:
“Thanks to this analysis, the researchers were able to narrow down their original list of 3,000 genes to 43 specific sequences that might have contributed to Lonesome George’s long, disease-free life.”