=9. A machine is supposed to fill soft drink cans to 12 ounces. It appears that although the average amount in the cans is about 12 ounces (based on sample means), there is a great deal of variability in each of the individual cans. The type of chart that would best detect this problem would be

a. a p-chart.

b. an R-chart.

c. a c-chart.

d. an attribute chart.