Answer:
(d) -- see attached
Explanation:
A graph that shows exponential decay is one that tends toward a horizontal asymptote as x gets large.
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A basic (parent) exponential decay curve is concave upward and tends toward zero as x gets large. The fractional change in any interval is the same as for any other interval of equal size. The curve attached decreases by a factor of 2 when x increases by 1.