The correct option is Authorizing official.

Authorizing official is the senior organizational official who has the formal authority to accept risk and to make the authorization decision for an information system. That authority requires defining what is inside the system and what is outside the authorization boundary so that the official can evaluate and accept residual risk for operation.

Chief Security Officer is incorrect because the CSO provides enterprise security direction and oversight but typically does not have the formal authority to define an individual system's authorization boundary or to make the authorization and risk acceptance decision.

System owner is incorrect because the system owner is responsible for day to day management and maintenance of the system and for ensuring security controls are implemented. The system owner often helps identify scope but normally does not have the final authority to formally authorize operation and accept organizational risk.

Chief Information Officer is incorrect because the CIO governs enterprise IT policy and strategy and may set standards for authorization, but the CIO does not usually perform the specific authorization decision or formally establish the authorization boundary for a particular information system.

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