A first grade teacher is concerned about a six year old girl in her class who has not spoken a single word since school started. The little girl participates appropriately in the class activities and uses gestures and drawings and nods and shakes her head to communicate. The parents report that the little girl talks only in the home and only in the presence of her closest relatives. Which of the following is the most likely diagnosis?
a) Autism,
b) Expressive language disorder,
c) Social phobia,
d) Selective mutism