A teacher wants to know whether the scent of citrus in the classroom influences students' performance on the SAT math test.

During a first-period class, the teacher administers the test as usual with no fragrance in the room and records the students' scores.

During the second period, a different group of students enter the room. The teacher sprays the room with a citrus fragrance and administers the same math test. The teacher records the students' scores.

In this study, what is the independent variable and what is the dependent variable?

A. The independent variable is the teacher's first-period class, and the dependent variable is the second-period class.

B. The independent variable is the classroom, and the dependent variable is the teacher.

C. The independent variable is the score on the math test, and the dependent variable is the citrus smell.

D. The independent variable is the citrus smell, and the dependent variable is the score on the math test.