Which set of ordered pairs could be generated by an exponential function?

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Which set of ordered pairs could be generated by an exponential function?
A. (1, 1) (2, 1/2) (3, 1/3) (4, 1/4)
B. (1, 1) (2, 1/4) (3, 1/9) (4 1/16)
C. (1, 1/2) (2, 1/4) (3, 1/8) (4, 1/16)
D. (1, 1/2) (2, 1/4) (3, 1/6) (4, 1/8)