A random sample of 121 bottles of cologne showed an average content of 4 ounces. It is known that the standard deviation of the contents (i.e., of the population) is 0.22 ounces. In this problem the 0.22 is

Select one:

a. a parameter.

b. the standard error of the mean.

c. a statistic.

d. the average content of colognes in the long run.