Little Billy’s dad takes his rattle. Little Billy does not cry or search for the rattle. Here, Little Billy has not developed:

Object permanence

Explanation:

Object permanence is a developmental stage in infants in which they become less worried about missing items due to their belief of the object being in existence even though they can’t see it.

Little Billy’s dad took his rattle and Little Billy does not cry or search for the rattle. This validates Little Billy being a child who has developed object permanence

answereruption of molten material; magnetic stripes in the rock of the ocean floor; the age of the rocks themselves;