Why Did Experimental Psychologists Ignore Emotion as a Research Topic

Why did experimental psychologists ignore emotion as a research topic for much of the 20th century?

A) Emotion was not considered an important aspect of human experience.
B) No theories of emotion had been proposed prior to the late 20th
Century.
C) Emotion was considered a completely subjective, internal experience that could not be studied with objective measures.
D) Experimental psychologists did not begin studying emotion until the technology was developed for studying brain activity during emotional experiences.