Final answer:
A private individual, a small charity, and a small business are all considered eligible complainants that can refer a complaint to the Financial Ombudsman Service (FOS).
So, all of the options (A, B, and C) may refer a complaint to the FOS as eligible complainants in the UK financial services context.
Step-by-step explanation:
The Financial Ombudsman Service (FOS) is an organization that helps resolve disputes between consumers and financial services providers. When it comes to referring a complaint to the FOS as an eligible complainant, there are several entities that may have this privilege.
These include a private individual, a small charity, and a small business. In business and legal terms, these entities can be directly involved in situations requiring the intervention of the FOS.
As an example, a private individual may refer a complaint if they feel they have been misled by financial advice, a small charity may do so if it encounters banking issues that were not handled satisfactorily, and a small business could refer a complaint regarding a financial product or service that affects its operations.