Final answer:
The correct answer is D. Pennsylvania. The Pennsylvania system, also known as the Philadelphia system, is characterized by silence and separation of inmates, aimed at self-reflection and reform.
Step-by-step explanation:
The style of penitentiary characterized by silence and separation of inmates is known as the Philadelphia or Pennsylvania system. This method was implemented to encourage reflection and change in prisoners through solitude and individual spiritual growth. The idea behind this was that inmates would use their time in silence to reflect on their crimes and reform their characters. The goal was for prisoners to reflect on their crimes and repent in isolation. Therefore, the correct answer would be D. Pennsylvania.