Answer:
d. the scientific basis of his theory that allowed predictions of future behavior.
Step-by-step explanation:
Freud as a renowed neurologist and who is perhaps most known as the founder of psychoanalysis was a great social scientist over the past few decades.
His study on emotional disorder known as hysteria helped him to discover the relationship between the symptoms and the traumatic experience which the patient passes through.
This observation had lead him to a major contibution in the scientific community with his theory used to predict future behaviour to be exhibited by an individual.