Explanation
Correct answer: A.
Choice A is the best answer. “Though” logically signals that the information in this sentence—that Morgado and colleagues detected a dense ring orbiting outside the Roche limit that remained intact—presents an exception to the previous sentence’s claim about debris orbiting outside an object’s Roche limit. Such debris would be expected to accrete into a satellite, not remain intact as a ring.
Why the other choices are wrong
Choice B
Choice B is incorrect because “for example” illogically signals that the information about Morgado’s discovery exemplifies the previous sentence’s claim about debris orbiting outside an object’s Roche limit. Instead, the sentence presents an exception to the claim.
Choice C
Choice C is incorrect because “fittingly” illogically signals that the information about Morgado’s discovery aligns with the previous sentence’s claim about debris orbiting outside an object’s Roche limit. Instead, the sentence presents an exception to the claim.
Choice D
Choice D is incorrect because “likewise” illogically signals that the information about Morgado’s discovery is similar to the previous sentence’s claim about debris orbiting outside an object’s Roche limit. Instead, the sentence presents an exception to the claim.