Logistic growth of a population size occurs when resources are limited.The formula we use to calculate logistic growth adds the carrying capacity as a moderating force in the growth rate.
The logistic model is given as dN/dt = rN(1-N/K)
When the value of N/K is one, then,
dN/dt = rN(1-N/K)
dN/dt = rN(1-1)
dN/dt = rN(0)
dN/dt = 0 (zero)
So, the growth rate of population will be equal to zero, when the value of N/K is equal to zero.
Thus, the correct answer is option A.