The correct answer is 2 – Shoulder dystocia - a common cause of brachial plexus injury during childbirth. In this particular case, the result was what is referred to as Erb's palsy, where the upper brachial plexus is compressed against the first rib as the baby's head passes through the birth canal but the shoulders become stuck behind the mother's pelvic bone.
There is no information to suggest a traumatic brain injury and although thoracic outlet syndrome does involve the brachial plexus it would not be the most accurate diagnosis for a patient of this age