Answer:
a) Environment
Step-by-step explanation:
In the heredity-versus-environment debate one side argues that the behavior of animals is the caused by genetic factors whereas the other side argues that the behavior of animals is the caused by environmental factors.
This debate is also called the nature versus nurture debate.
In terms of personality research of twins and adopted children indicate that twins share more personality traits in common than the adopted children. This makes the genetics argument stronger.