Why Are Measures of Association Helpful in Testing the Validity

Why are measures of association helpful in testing the validity of a theory?

A) Theories do not specify what the independent or dependent variable is in a relationship, so measures of association help clarify this point.
B) Theories seldom articulate cause-and-effect relationships, so measures of association help determine causality.
C) Theories stipulate that one variable causes another, so we need to know how strongly the independent variable is related to the dependent variable.
D) Measures of association are not helpful in testing a theory; they are used for research purposes where theory is not yet developed.