When Minerva's parents attended the parent-teacher conference held at the end of the second month her first-grade school year, they learned that their daughter never spoke in class. Her teacher noted that she did speak on the playground and in the lunchroom, but she was utterly silent in class and would not say a word even when called on. Minerva's parents were surprised since they knew their daughter to be quite verbal at home with family and friends. What diagnosis is most consistent with Minerva's behavior?