The fact that Abigail was able to look for the toy after it feel was a result of her developing object permanence.
This is an ability that humans develop as children where they are able to understand that other people and objects exist around them.
Abigail was able to understand that the toy existed which was why she began to look for it when it fell out of her crib.
In conclusion, option D is correct.
Find out more on Object permanence at https://brainly.com/question/4667602.
