Explanation
Consistent security is the primary reason for integrating the various assurance functions of an organization for the information security manager because it ensures that the security policies and standards are applied uniformly and effectively across different domains, processes, and systems of the organization.
Comprehensive audits are not the primary reason for integrating the various assurance functions, but rather a possible outcome or benefit of doing so. A security-aware culture is not the primary reason for integrating the various assurance functions, but rather a desirable state or goal of the organization. Compliance with policy is not the primary reason for integrating the various assurance functions, but rather a basic requirement or expectation of the organization. References:
https://www.isaca.org/resources/isaca-journal/issues/2016/volume-4/integrating-assurance-functions
https://www.isaca.org/resources/isaca-journal/issues/2017/volume-3/how-to-measure-the-effectiveness-of-your-i