The domain of a function or a graph is the set of all possible x-values or inputs. In the context of this problem, we are looking at a graph that represents a relationship between the number of cookies sold (the x-axis) and the earnings in dollars (the y-axis).
The cost of the baking supplies and the number of charity organizations supported are factors, but they are not directly related to the input (x-values) or output (y-values) of the graph function. Hence, they are not part of the domain or range of the function.
Therefore, the domain of this graph function is the number of cookies sold (option A), as this variable is represented along the x-axis and constitutes all possible inputs to the function.
Remember, the domain is all the possible input or x-values, and in this case, it is the number of cookies that can be sold.