According to the Certified Information Security Manager (CISM) Study Manual, risk owners are responsible for managing a risk, including taking corrective action to reduce the risk to an acceptable level. When implementing controls, it is essential to obtain input from risk owners to ensure that the controls are effective in managing the risk to an acceptable level.
By obtaining input from risk owners, the organization can ensure that the controls are tailored to the specific risks and are effective in reducing the risk to an acceptable level. This can help to minimize the impact of the risk on the organization and reduce the potential for financial or reputational damage.

The explanation given in the manual is:
Incident classification criteria enable an organization to prioritize incidents based on their impact and urgency. This allows for an optimized allocation of recovery resources to minimize business disruption and ensure timely restoration of normal operations. The other choices are benefits of incident management but not directly related to incident classification criteria.

Residual risk is the remaining risk after all security controls have been implemented. It is important to measure the residual risk of an organization in order to determine the effectiveness of the security program and to justify continued investment in the program. A reduction in residual risk is an indication that the security program is effective and that continued investment is warranted.

Reviewing the vendor contract should be the information security manager's first course of action when discovering an HVAC vendor has remote access to the stores to enable real-time monitoring and equipment diagnostics. The vendor contract should specify the terms and conditions of the vendor's access to the retailer's network, such as the scope, purpose, duration, frequency, and method of access. The vendor contract should also define the roles and responsibilities of both parties regarding security, privacy, compliance, liability, and incident response. Reviewing the vendor contract will help the information security manager to understand the contractual obligations and expectations of both parties, and to identify any gaps or issues that need to be addressed or resolved1. The other options are not the first course of action for the information security manager when discovering an HVAC vendor has remote access to the stores. Conducting a penetration test of the vendor may be a useful way to assess the vendor's security posture and potential vulnerabilities, but it should be done with the vendor's consent and cooperation, and after reviewing the vendor contract2. Reviewing the vendor's technical security controls may be a necessary step to verify the vendor's compliance with security standards and best practices, but it should be done after reviewing the vendor contract and in accordance with the agreed-upon audit procedures3. Disconnecting the real-time access may be a drastic measure that could disrupt the vendor's service delivery and violate the vendor contract, unless there is a clear and imminent threat or breach that warrants such action. Reference: 1: Vendor Access: Addressing the Security Challenge with Urgency - BeyondTrust 2: Penetration Testing - NIST 3: Reduce Risk from Third Party Access | BeyondTrust : Third-Party Vendor Security Risk Management & Prevention