Which of the Following Research Methods Did the Masters and Johnson

Which of the following research methods did the Masters and Johnson team primarily use for conducting their studies on human sexual behavior?

A) They implemented participant-observation techniques that examined human behavior in its own cultural context.
B) They implemented a treatment approach that primarily focused on the unconscious mind and "talking therapy".
C) They implemented a treatment approach that primarily focused on differentiating normal and abnormal behavior in sexuality.
D) They implemented a laboratory method for the study of orgasm and sexual functioning.
E) They implemented the scientific survey study,using a questionnaire to reveal the sexual attitudes of a large number of people.