Answer:
C
Explanation:
We know that the initial population was 2,400 black rhinos.
And we also know that they are declining at a rate of 10% per year.
In other words, each subsequent year will only have 100% - 10% or 90% of the previous year's rhinos.
Therefore, we can write the following function:

Next, we can eliminate some choices.
First, the starting point (the y-intercept) must be 2,400 because that's the number of rhinos we started out with.
Therefore, we can eliminate A and D.
From the remaining choices B and C, we can also eliminate B. This is because from our function, we know it's exponential decay, and exponential decay is not a straight line.
However, to double check, let's check the population after 10 years using our function. So.

Use a calculator:

So, after 10 years, the population should be around 840.
At x = 10, B is not around 840. However, C is right around it.
Therefore, we can conclude that C is the right answer.