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

a (-1,-1/2), (0, 0), (1,1/2), (2, 1)
b (–1, –1), (0, 0), (1, 1), (2, 8)
c (-1,1/2) (0, 1), (1, 2), (2, 4)
d (–1, 1), (0, 0), (1, 1), (2, 4)

By visually assessing we can eliminate the other choices until we have the ff: 

(–1, –1), (0, 0), (1, 1), (2, 8)(–1, 1), (0, 0), (1, 1), (2, 4)
Well, it's definitely not the second set of points.  Exponential functions are monotonic (either always increasing, or decreasing).  In the second set, the function has decreased from (-1,1) to (0,0), and then increased from (0,0) to (1,1).