To determine which function represents exponential decay, you should look at the base of the exponent in each function. For exponential decay:
Base 0 < b < 1 : The function will demonstrate exponential decay because as x increases, y decreases.
A.
Base: 4.09 (greater than 1)
Behavior: Exponential growth. As x increases, y increases.
B.
Base: 0.97 (less than 1)
Behavior: Exponential decay. As x increases, y decreases.
C.