Eliminating A and C

Hi Samlhoover, thanks for the question. This is an interesting question. I think mainly because of how short it is and how simple it should be considering it is just two lines of conditional reasoning. But they phrased the relationship between Xian and Chengdu in a rather confusing way, IMO. Personally, the confusion for me stemmed from the fact that there is a map in my mind of where the flights must go and in which order. However, we are not ordering these items, we are making conditional diagrams for them. So, when they said that Xian must come before Chengdu, for a moment I was confused about how to draw this in, but then it struck me that in saying this, they are stating that Xian is necessary for Chengdu. Very odd. But once we get past this idea, it becomes very, very straightforward. I hope I didn't lose you with this blurb. The conditional diagram for this passage is drawn as follows: Lhasa - > Chengdu - > Xian (In essence, A - > B - > C) It then concludes, that in order to get to Lhasa, you cannot avoid Xian (in other words, it is concluding A - > C) Answer choice A has several differences in its structure compared to the reasoning in the passage. Namely, the "or" as you mentioned, the "most", and the "likely". Answer choice C is also incorrect for the exact reason you mentioned. I hope this helps. Please let me know if you have any other questions!