Natural Experiments _____ Specify Cause-And-Effect Relationships Because _____

Natural experiments _____ specify cause-and-effect relationships because _____.

A) can; the study has both an independent and a dependent variable
B) can; the experiment takes place in the natural environment
C) cannot; the experimenter cannot control assignment of subjects to treatments
D) cannot; the natural event to which subjects are exposed (that is, independent variable) may be artificial or contrived