Final answer:
The base of the provided exponential function is 0.6394, and since it is less than one, it represents a decay factor. Therefore, the correct answer is option c).
Step-by-step explanation:
The equation of an exponential function provided is N = 20.5(0.6394). In the exponential function N = ab, the base b represents the constant ratio by which the function grows or decays each step. The initial amount before any growth or decay occurs is represented by a. In this equation, the base b can be identified as 0.6394, which is the factor that the quantity N is being multiplied by to determine its next value.
Because the base b is less than 1, this signifies a decay factor, not a growth factor. Each step, the amount is being multiplied by a number less than 1, which means it is getting smaller. Therefore, the correct answer is c) b = 0.6394, decay.