Which types of firms does the FCA conduct regulation for?

The Financial Conduct Authority (FCA) is responsible for regulating a broad spectrum of firms to ensure that financial markets operate fairly and effectively. This includes all regulated firms, which consists of a wide array of businesses operating in the financial services sector, ranging from banks and building societies to insurance companies, investment firms, and even certain aspects of consumer credit providers. The FCA's role extends beyond just the firms that are dual-regulated by both it and the Prudential Regulation Authority (PRA).

By regulating all types of firms, the FCA aims to protect consumers, enhance the integrity of the UK financial system, and promote competition among financial services providers. This comprehensive regulatory approach allows for a more stable and transparent financial environment, benefiting both consumers and the economy at large.

The other choices specify limitations that do not align with the FCA's mandate. For instance, only focusing on dual-regulated firms or non-regulated firms would ignore significant segments of the financial services market that the FCA oversees. Similarly, restricting regulation solely to retail firms would overlook the important roles of institutional and wholesale firms in financial markets. Thus, the correct answer accurately reflects the extensive scope of the FCA's regulatory responsibilities.