Which unifying theme is reflected by Rhianna's use of research to investigate her ideas about human behaviour

A)  Psychology is theoretically diverse. 
B)  Psychology is empirical. 
C)  Behaviour is shaped by cultural heritage. 
D)  People's experience of the world is highly subjective.

Empirical

Pertaining to or based on observation or experience rather than theory or pure logic.

Investigate

the action of carrying out research or systematic inquiry to discover facts or information about a subject, often involving the collection of evidence.

Human Behaviour

The range of actions, conduct, and responses exhibited by humans, influenced by culture, attitudes, emotions, values, ethics, and the external environment.