A plot or graph shows the relationship between related variables.
The best graphic to use is the residual plot.
The best graph to plot a linear regression is the scatter plot, because it shows a clear relationship between the variables that are being compared.
From the list of given options, we can say that the residual plot is the best plot to use by the consultant.
This is because, the residual plot is a form of scatter plot that shows the difference between the observed value and the actual value.
In this case, the observed value would be the number of units sold, while the actual value would be the expected number of units to be sold.
Hence, option (c) answers the question.
See attachment for an illustration of the residual plot
Read more about residual plots at:
https://brainly.com/question/2876516
