To Evaluate the Objectivity of a Certain Professor's Grading,20 Classes

Multiple Choice

To evaluate the objectivity of a certain professor's grading,20 classes that she previously taught are randomly selected for auditing.The proportion of male students that pass in each class is compared to the proportion of female students for each selected class.The sample in this study is:

A) the comparison of male and female passing rates for the classes.
B) the proportion of all males that passed and the proportion of all females that passed.
C) the 20 selected classes.
D) a single selected class.