A passenger cannot land in Ulan Batur without first landing in Ethiopi

Please anyone help me explain why it is not B?
Thanks a lot in advance!

yenngoc2409 From the stimulus, we know two things: 1) If a passenger landed in Ulan Batur, then they landed in Ethiopia and 2) If a passenger landed in Ethiopia, then they landed in Republic. B incorrectly assumes that just because a passenger did not land in Ethiopia, it is impossible for him/her or "must not have" landed in the Republic. However, it's possible that he/she landed in the Republic without having gone to Ethiopia at all. Maybe we went to the North Pole first... Therefore, this statement is a possibility but not a definitive truth. (According to the Powerscore method, this would be considered a "mistaken negation".)

The negation concept is probably easier to understand outside of this context...because this whole country/region thing is confusing! For example, let's say that the original statement was: If you eat 5 pies, then you'll be sent to the hospital. If we negate this (the way B does with the original post), it'd say: If you did not eat 5 pies, then you must not have been sent to the hospital. Logically speaking, this looks "in line" with the original statement but is negated and makes 0 sense. Just because I didn't eat 5 pies, doesn't mean I didn't go to the hospital. What about getting sick? Visiting a friend?

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