Passage B doesn’t discuss the discovery of Uranus. It discusses the discovery of Neptune.

The last sentence of passage A says negative evidence is rarely conclusive in disproving a theory. The discussion of Uranus in passage B supports that claim by giving an example where negative evidence was obtained, but that evidence didn’t disprove a theory. Observations of Uranus’s orbit contradicted what Newton’s laws said should happen. This was negative evidence against Newton’s laws. But the problem wasn’t actually that Newton’s laws were wrong. The problem was just that an overlooked planet (Neptune) was affecting the orbit. Once that planet was accounted for, everything aligned with Newton’s laws.

This anti-supports the last sentence of passage A, which says negative evidence is rarely conclusive in disproving a theory. But the discussion of Mercury is an example of negative evidence succeeding in disproving a theory. Observations of Mercury’s orbit contradicted what Newton’s laws said should happen. This was negative evidence against Newton’s theory, and cause scientists to doubt and ultimately reject that theory.

This anti-supports the last sentence of passage A, which says negative evidence is rarely conclusive in disproving a theory. But the discussion of Mercury, and the associated failure to find Vulcan, is an example of negative evidence succeeding in disproving a theory. Observations of Mercury’s orbit contradicted what Newton’s laws said should happen. This was negative evidence against Newton’s theory. There were two explanations: maybe Newton’s laws are just wrong, or maybe “planet Vulcan” is throwing off the calculations. But Vulcan was never found, and scientists concluded that Newton’s laws were indeed wrong. In other words, the failure to find Vulcan ruled out an alternative hypothesis about what the negative evidence signified, and so helped to disproved a theory.

The last sentence of passage A says negative evidence is rarely conclusive in disproving a theory. In other words, we’re trying to support the idea that negative evidence doesn’t always disprove theories. But (E) is an example of positive evidence helping to prove a theory. (Observations of Mercury’s orbit matched what Einstein’s theory predicted, and so those observations were positive evidence of that theory.)