At One Time, Psychologists Had to Rely on the Subjective

At one time, psychologists had to rely on the subjective reports of people who said that they never dream. When the EEG was invented, it was found that everyone dreams every night. Thus, until the invention of the EEG, sleep and dreaming were not objectively studied because

A) it was unethical to watch people sleep.
B) it was not considered a suitable TOPIC (B-HEAD) for psychological research.
C) there was not a suitable research method available to study the TOPIC (B-HEAD) .
D) there was a lack of interest in understanding sleep and dreaming.