One Explanation for Why Siblings Growing Up in the Same

One explanation for why siblings growing up in the same family have such different experiences in their nonshared environment is that

A) each sibling is born into the family at a different point in the family's timeline.
B) the quality of the genetic inheritance each sibling receives is degraded with each subsequent birth.
C) parents are less invested in the well-being of their later born children.
D) the quality of the family's lifestyle improves with each subsequent birth.