Process of elimination helped me figure out why I got this wrong:
B and C: These have nothing to do with disproving Newton's Theory, which is a part of the last paragraph, which the question centers on
D: Venus isn't even in the passage. They probably used it to confuse us with 'Vulcan.'
E: The only time the sun is mentioned is in the first paragraph as an auxiliary function, whereas the black swan in passage A is used as the main evidence to disprove a theory.
A is the correct answer because Mercury's orbit disproved the Newton's theory just like the black swan disproved the theory that there are no white swans
