Final answer:
Option d) f(x) = 6 * (1/3)^x represents exponential decay because it has a base of 1/3 that causes the function to decrease as x increases.
Step-by-step explanation:
An example of exponential decay in the provided options is d) f(x) = 6 * (1/3)^x. In exponential decay, the base of the exponent is between 0 and 1, which means the function's value decreases as x increases. Comparing the provided options, option d) has a base of 1/3, which satisfies this condition, hence it represents exponential decay.