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Refer to the figure below.

Which of the following equations could represent the graph of this figure?

$ f(x) = - \sin {8x} $

$ f(x) = \sin \cfrac{1}{8}x $

$ f(x) = \cos(\cfrac{8x-\pi}{2}) $

$ f(x) = \cos (\cfrac{1}{8}x - 2\pi) $

$ f(x) = cos(8x-4\pi) $