Answer:
The concept which best describes the change of the population is the derivative of 
.
Explanation:
Observe that the function 
 describes the amount of rabbits at the time t (in years) but no the rate of change of the population at a given instant. So you have to use the derivative of 
 to obtain that rate of change at any instant. For example, if we derivate the function 
 we obtain:

And if we want to find the rate of change at 
 years we evaluate
 rabbits/year