A Texas school district wants to compare the effectiveness of a standard AP Statistics curriculum and a new "hands-on" AP Statistics curriculum. Two experienced teachers, Mr. Pryor and Mr. Legacy each teach one class with the standard curriculum and one with the new approach. Students are assigned at random to these four classes. At the end of the year, all students take the AP Statistics exam. The subjects in this experiment are
A. Mr. Pryor and Mr. Legacy.
B. the two AP Statistics curricula.
C. the students in the four classes.
D. all students taking AP Statistics in Texas.
E. only one: AP Statistics.
Answer: C