Answer: Option 'D' is correct.
Explanation:
Since we have given that
Initial population of rabbits = A = 6
Each year, there were 4 times as many rabbits as the year before.
i.e. b = 4
Let the number of years be x.
So, our required equation will be
![f(x)=Ab^x=6(4)^x](https://img.qammunity.org/2019/formulas/mathematics/high-school/cg39xs68tjcmsjklggwit2prt7447rvh27.png)
Hence, Option 'D' is correct.