Theory or a System of Explanation Rests Upon the Condition

Theory or a system of explanation rests upon the condition that

A) unobservable constructs are defined solely in terms of unobservable constructs.
B) there is a strong relationship among the observable constructs.
C) the relation between x and y can be captured with a linear model.
D) at least some of the constructs can be operationalized and measured.
E) observable constructs are defined solely in terms of unobservable constructs.