6) In question 4, you estimated the time for lowering the surface of Happy Valley enough to account for the modern difference in elevation between the top of Mount Nittany and the bottom of the valley. In question 5, you saw that you could change that estimate a good bit. But, to make a 10-fold change in the estimate, you had to assume things that are really almost impossible, such as making central Pennsylvania one of the wettest places on Earth. We could tweak the assumptions in the calculation to move the estimate either way by a few-fold (so 10 million years could become 3 million years, or 30 million years, without too much trouble), but shifting the answer a whole lot further than that requires impossibilities or miracles-- just because we can shift it to 3 million years or even 1 million years does not mean we can shift it to 10,000 years, which would require digging the valley 1,000 times faster than is happening now, which nature really cannot do here. We can say something else important, though. Whatever the time needed for deepening the valley, the geologic story of central Pennsylvania must be much longer than that--time-deepening the valley is only the last act of a long play. The text of this exercise refers to several reasons why we know that the story is longer than the deepening of the valley. Which two statements below describe something indicating that the region is much older than calculated so far in this exercise? A) The mountain top is being eroded as well as the valley, so more rock must have been removed from the valley than you calculated to give the modern difference in elevation between mountain top and valley. B) Just because. C) Mountains are always old. D) \"Clams got legs\