People who say that Dooney County is flat are clearly wrong. On flat land, soil erosion by water is not a problem. Consequently, farmers whose land is flat do not build terraces to prevent erosion. Yet I hear that the farms in Dooney County are dotted with terraces. The author's conclusion in the passage depends on the assumption that
A: on flat land there is no soil erosion
B: the only terraces in Dooney County are on farmland
C: there are terraces on farmland in Dooney County which were built to prevent soil erosion
D: the only cause of soil erosion is water
Choose A, B, C or D as your solution.
C