The diagrams below illustrate models of various chemical compounds..

How do the test variables (independent variables) and outcome variables (dependent variables) in an experiment compare?
A. The outcome variable (dependent variable) controls the test variable (independent variable).
B. The test variable (independent variable) controls the outcome variable (dependent variable).
C. The test variable (independent variable) and outcome variable (dependent variable) have no affect on each other.
D. The test variables (independent variables) and outcome variables (dependent variables) are the same things.