A study was designed to determine how test scores on a 20-question test were related to the time spent studying for the test. 

What are the independent and dependent variables for this study?  
A.The independent variable is time spent studying, and the dependent variable is the number of questions on the test.  
B.The independent variable is the score on the test, and the dependent variable is the number of questions on the test.  
C.The independent variable is time spent studying, and the dependent variable is the score on the test.  
D.The independent variable is the score on the test, and the dependent variable is time spent studying.