Final answer:
Thornberry's interactional theory attributes delinquency to interactional dynamics, emphasizing the interplay between individual traits and social relationships as the key cause of delinquent behavior.
Step-by-step explanation:
According to Thornberry's interactional theory, the fundamental cause of delinquency is D. Interactional dynamics. Thornberry's theory emphasizes that delinquency is a result of interactions between individual characteristics and social experiences.
More specifically, it recognizes how personal traits interact with social relationships and structures over the life course of an individual to influence behavior. This theory differs from, but is complementary to, other theories such as social control theory, which focuses on the strength of social bonds and how their absence can lead to deviant behavior,
or social disorganization theory that attributes crime to weakened social ties and lack of social control in a community. Therefore, Thornberry sees the interplay between multiple factors—or interactional dynamics—as the key contributors to delinquent behavior.