Your text's two unifying themes of "our behaviour is shaped by our cultural heritage" and "heredity and environment jointly influence behaviour" both describe more specialized statements of which other theme

A)  Psychology evolves in a sociohistorical context. 
B)  Psychology is theoretically diverse. 
C)  People's experience of the world is highly subjective. 
D)  Behaviour is determined by multiple causes.

Cultural Heritage

The legacy of physical artifacts and intangible attributes of a group or society passed from one generation to another, including customs, practices, places, objects, artistic expressions, and values.

Heredity

The transmission of physical or mental traits from parents to their offspring through genetics.

Behaviour

The actions or reactions of an individual, usually in relation to the environment, which can be observed and measured from an objective standpoint.