Can someone explain why 2 is the correct choice

A gradient graph (derivative) representing the state of a dynamic equilibrium in a population should be a constantly straight (horizontal linear) line. Option 1 shows a increase which means it hasn't reached dynamic equilibrium. Option 2's average at all times is a constant number, which it fluctuates to maintain equilibrium. Option 3 shows a generally increasing trend, meaning the population is not balanced. Option 4 is plainly something that doesn't make sense as it is all over the place.

As the data points on Option 2 fluctuate around a certain value, it can be seen that Option 2 is the graph representing the state of a dynamic equilibium in the population.