The primary function of an operational risk committee is to oversee, manage, and report a comprehensive picture of the company's operational risks to the executive risk committee, management committee, and board risk committee. This involves coordinating with various levels of the firm's decision-making hierarchy and ensuring that relevant information is escalated to the appropriate committees. The operational risk committee plays a crucial role in the company's risk management structure by providing a holistic view of operational risks, which enables the executive risk committee and the board risk committee to make informed decisions about risk mitigation strategies and policies.

Choice B is incorrect. While an operational risk committee may oversee the activities of a specific business line or function, this is not its primary function. The main role of the operational risk committee is to oversee, manage and report on all operational risks to the executive risk committee.

Choice C is incorrect. Although overseeing all operational risks might seem like a plausible answer, it's not entirely accurate. The primary responsibility of an operational risk committee isn't just oversight but also managing and reporting these risks to the executive risk committee.