Why might an infant develop an insecure attachment to his caregiver?

A The caregiver performs routine tasks in a predictable order.
B The caregiver does not respond to the baby's smiles and cries, or reacts unpredictably: sometimes happily, and sometimes with anger.
C Insecure attachments are almost always the result of abuse or trauma.
D.The caregiver is loving, consistent, and responsive to the infant's needs.