Answer:
a. independent variable.
Step-by-step explanation:
The effect of the room, in which the students study is being measured on the basis of their performance on the test.
The room in which the students study changes irrespective of their performance in the test.
However, the performance of the students is being compared between the students who studies in the classroom and the library. The performance should change with respect to the rooms they study in.
Hence, the performance is the dependent variable and the rooms where students study is the independent variable.