user
A doctor walked into the store and said hello son.  The boy looked at the doctor but did not say hello father.  Why is this?
A: spouse
B: nurses
C: medication
D: doctor was boys mother
E: great grandfather
assistant
<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

D

<|end_of_solution|>