A scatter plot would be useful for

A. Showing the relative number of sales of four different brands of blank DVDs
B. Showing the trend of sales, over time, of five different brands of blank DVDs
C. Showing the relationship between the sales of blank CDs and blank DVDs
D. Showing the top selling brands of blank DVDs

C.

A scatterplot is a useful summary of a set of two variables. It gives a picture of the relationship between the two.

A scatter plot would be useful for option C: showing the relationship between the sales of blank CDs and blank DVDs.

A scatter plot would be useful for showing the relationship between two variables. It displays data points as markers on a Cartesian coordinate system, with one variable represented on the x-axis and the other variable represented on the y-axis.

Looking at the options, we can eliminate options C and D. Option C involves comparing sales of blank CDs and blank DVDs, which would require a different type of plot such as a bar chart or line graph. Option D involves showing the top selling brands, which would typically be better represented with a bar chart or a pie chart.

Now, let's consider options A and B. In option A, we have four different brands of blank DVDs, and we want to show the relative number of sales. Since we are comparing different brands, a scatter plot wouldn't be the most appropriate choice. Instead, a bar chart or a stacked bar chart could be used to show the sales of each brand side by side.

Option B involves showing the trend of sales over time for five different brands of blank DVDs. This scenario fits well with a scatter plot. Each data point on the plot would represent the sales of a particular brand at a specific time. By connecting the data points, we can observe the trend and identify any patterns or relationships between time and sales for each brand.

Therefore, the correct answer is B. A scatter plot would be useful for showing the trend of sales, over time, of five different brands of blank DVDs.