Which of the Following Researchers Is Using an Acceptable Operational

Which of the following researchers is using an acceptable operational definition of a variable?

A) Dr. Ziggy defines aggression as how angry one feels in different situations.
B) Dr. Abrams defines embarrassment as the number of friends on Facebook.
C) Dr. Byrne defines intelligence as one's score on the Wechsler Adult Intelligence Scale.
D) Dr. Clay defines attraction to another as the desire to be liked by the other.