Tammy's father is an exceptional gymnast. When Tammy was just a toddler, her father believed that Tammy already showed great promise as a gymnast. Tammy's father probably believes that athletic ability is mostly determined by

Answer: Nature

Explanation:

Tammy's father being a great gymnast believes that Tammy would also become one. Hence he tends to see this attributes in Tammy even though she is still a toddler. He believes that Tammy being his daughter would naturally become a gymnast like him.