The correct choice for a reasonable domain for the function is option (b) 0 ≤ x ≤ 31.
How to determine the reasonable domain for the function
To determine the reasonable domain for the function f(x) = 100(1.05)x
Given that the function represents the number of fish in the river after x days in the month of October, we can reasonably assume that the maximum number of days in October is 31.
Therefore, option (b) 0 ≤ x ≤ 31 is a reasonable domain for the function.
In this case, x represents the number of days in October, and it ranges from 0 to 31 because the population is being tracked and modeled specifically for the month of October.
Therefore, the correct choice for a reasonable domain for the function is option (b) 0 ≤ x ≤ 31.