Answer:
B. F. Skinner was a radical behaviorist who refused to speculate about what happens inside an organism.
Step-by-step explanation:
B. F. Skinner was an American psychologist and behaviorist, to this day considered to be very influential. Some of his principles are still applied at schools, businesses, and even prisons. To properly complete the sentence "B. F. Skinner was a radical behaviorist who refused to," we must take a look at his methods and beliefs.
We can eliminate the first option, since Skinner did conducts studies with animals (a rat, for example). He did not refuse to believe in observation; quite the opposite, he believed the environmental causes of behavior could always be observed. That eliminates the second option as well. Also, he did not refuse to believe in or accept change. In fact, his principles and methods were and still are greatly used to teach and change behaviors via reinforcement.
We are left with the last option, and the only correct one. Skinner's approach was nicknamed "empty organism". He refused to speculate what happens inside an organism. His only concern was with measurable environmental events and measurable behaviors. Whatever could be happening inside the subject of observation - feelings, thoughts, perceptions - was not taken into consideration.