If there are no limiting factors a population can reach its A) competition level
B) population potential
C) population density
D) biotic potential

I am not sure but think that the answer should be population density.

Limiting factors determine the carrying capacity of a population. Recall that when there are no limiting factors, the population grows exponentially. In exponential growth (J-shaped curve, curve A: Figure below), as the population size increases, the growth rate also increases.