Jack and Jill Are Twins

Multiple Choice

Jack and Jill are twins. Because he is a boy, Jack's parents encourage him to run. However, they discourage Jill from engaging in athletic activity. As a result, Jack is much faster at running up a hill than Jill. The difference in Jack and Jill's behavior is best explained by

A) nonshared environmental influences.
B) active gene-environment relations.
C) polygenetic effects.
D) niche-picking.