Which of the Following Is TRUE

Which of the following is TRUE?

A) A constitutive definition describes how a construct is to be operationalized.
B) In general, a researcher should start with observable, operational definitions and then proceed to conceptually define the construct or constructs that have been measured.
C) A theory based completely on conceptual definitions of constructs is circular and cannot legitimately be considered a theory.
D) a and b.
E) a, b, and c.