Input: The earth is flat.
(A) If you walk really far from a tall building on earth you will no longer see the bottom part of it while on a flat surface this would not happen.
(B)If you get a flat tire you could either replace it yourself or ask someone to help you and some nice person from earth will probably assist.
(C)If you walk really far from cities on earth and lay flat on your back and watch the night sky you'll be amazed by all the stars you would see.
Output: A