We have to select a point that is the best representative of the square root of 15.
We can calculate the square root of 15 with a calculator, but we can aproximate with the following reasoning.
We know that 15 is the product of 3 and 5. If we average them, we have 4.
If we multiply 4 by 4, we get 16, that is a little higher than 15.
If we go to the previous number (3) and calculate 3 by 3 we get 9, that is far from 15 than 16.
So we can conclude that the square root of 15 is a number a little less than 4.
In the graph, the point B is the one that satisfy our conclusion, as it is a point in the scale that is between 3 and 4, and closer to 4.
The answer is Point B