Which of the following actions could lead to charges of official oppression?

Charges of official oppression could stem from actions that involve the abuse of power or authority, particularly in a way that infringes on the rights of individuals. Refusing necessary medical treatment to inmates falls under this category because it involves neglecting a legal and ethical duty to provide adequate healthcare, thereby violating the rights of the inmates to receive appropriate medical care. This refusal can result in severe health consequences for the individuals involved, making it an abuse of power.

In contrast, providing medical care and allowing inmate visits are actions that typically fulfill an officer's responsibilities and legal obligations. Submitting reports on time is also an administrative duty that would not lead to charges of oppression. The key element in the correct answer is the refusal of necessary medical treatment, which embodies a clear misuse of authority and disregard for inmate welfare.