Which of the following structures requires registration with the Registrar of Companies?

A private limited company is required to register with the Registrar of Companies because it operates as a separate legal entity from its owners. This registration process is essential for the formation of the company and provides legal recognition, allowing it to enter contracts, own assets, and be liable for its debts. The registration also involves submitting necessary documentation, such as the Articles of Association and the Memorandum of Association, which outline the company's structure, purpose, and operational rules.

In contrast, sole traders and partnerships do not require formal registration with the Registrar of Companies to operate. While they may choose to register their business name or obtain certain licenses, these structures fundamentally belong to the individuals running them, and liability for debts lies with the individual partners or sole trader. The public sector typically refers to government entities and does not require registration in the same way businesses do, as they are managed by the government and funded by public resources. Thus, the distinction lies in the legal recognition and structure that a private limited company necessitates through official registration.