Answer:
A. heredity has minimal effects on one's personality
Step-by-step explanation:
In the twin studies, researchers separate two twins and put them in different environment to grow. The purpose of this study is two find out whether they will grow up with different personalities.
As it turned out, the twins that separated and grew up in different environment still grow up with similar personalities. From this, researchers made the conclusion that heredity is actually has a huge effects of one personality (since twins born with identical genetics).