Final answer:
The issue described in the scenario is most significantly contributed to by the inmate's belief system/religion, as his dietary and prayer practices, integral to his Jewish faith, have been impeded.
Step-by-step explanation:
Among the options provided, the factor that most contributed to the issue described in the scenario is D. Belief system/religion. The inmate's complaint centers on the replacement of his Kosher meals with vegan meals and the restrictions on his ability to pray according to his faith. This is directly related to his religious rights and practices, as proven in the legal case Max Moussazadeh v. Texas Department of Corrections, which highlights the importance of accommodating religious practices within correctional facilities.
The changing dietary requirements impact his religious observance, and the limitations placed on his prayer location within his cell, due to the presence of a toilet considered unclean for prayer purposes, impacts his spiritual practice. The case underlines the significance of respecting and facilitating the belief systems of incarcerated individuals, as mandated by various laws and regulations.