Which of the Following Is True of Operational Definitions

Which of the following is true of operational definitions?

A) Conceptual definition and operational definition mean the same thing.
B) Popular press descriptions of research usually refer to the operational definitions.
C) Some psychological concepts are more difficult to operationally define than others.
D) Some psychological concepts cannot be operationally defined.
E) Operational definitions answer the question "Why did the researchers measure this variable?"