John Watson's rejection of introspection and insistence upon laboratory methods is consistent with which of your text's unifying themes

A)  Psychology is empirical. 
B)  Heredity and environment jointly influence behaviour. 
C)  People's experience of the world is highly subjective. 
D)  Psychology evolves in a sociohistorical context.

Empirical

Relating to knowledge or information gained through observation, experience, or experimentation rather than through theory or pure logic.

Introspection

Self-scrutiny of one's mental and emotional processes.

Laboratory Methods

Techniques and procedures used in the controlled settings of a lab to investigate phenomena, conduct experiments, and perform research across various scientific disciplines.