Attachment Behavior First Begins to Emerge in Infants Around 6

Attachment behavior first begins to emerge in infants around 6 months of age. Which of the following is the most commonly accepted reason for attachment developing at this age?

A) Infants' vision may become acute enough at this time to distinguish parents from other people.
B) Infants do not develop object permanence - the ability to remember that objects still exist when they are out of sight - until 6 to 9 months of age.
C) Infants begin to crawl around 6 to 9 months of age, and are at greater risk of getting hurt or lost.
D) All of the above explanations are commonly accepted.