Which of your text's unifying themes is emphasized by John Watson's proposal that psychology should study only observable behaviours and not consciousness

A)  Behaviour is influenced by multiple causes. 
B)  Psychology should use theories. 
C)  Psychology should be empirical. 
D)  People's experience of the world is highly subjective.

John Watson's proposal emphasizes the theme that psychology should be empirical, meaning that it should be based on objective observation of behavior rather than subjective experiences or consciousness. This theme highlights the importance of scientific evidence and data in making psychological claims and understanding human behavior.