Which of these must be observed when entering market orders according to trading regulations?

Observing the principle of dual control when entering market orders is essential for maintaining the integrity of the trading process. This principle mandates that no single individual should have sole control over the entire trading order process, which includes the creation, authorization, and execution of trades. By requiring dual control, trading regulations help to mitigate the risk of errors and fraudulent activities, ensuring that transactions are executed transparently and with accountability.

Implementing this principle creates a system of checks and balances, enhancing operational integrity and reducing the potential for misconduct. In practice, this may involve having one person enter the order while another person, or a different system, verifies it before execution. This dual oversight is especially vital in environments where high volumes of trading activity occur, as it can help identify and rectify issues before they escalate.

In contrast, the other options do not align with the regulatory framework designed to protect the trading environment and ensure proper oversight. For example, relying solely on market values or historical prices lacks the rigorous oversight that the dual control principle provides, while claiming that no checks are necessary would contradict the fundamental principles of risk management and compliance in trading activities.