The primary purpose of creating a security policy in a GitHub repository is to guide users and contributors on how to report security vulnerabilities in a responsible and secure manner. This policy outlines the preferred method of communication, timelines, and any other pertinent information related to handling security issues.

Security Policy:

Option C is correct because a security policy provides guidelines for responsibly disclosing security vulnerabilities. This helps maintainers respond to and address security concerns promptly and securely, thereby protecting the project and its users.

Incorrect Options:

Option A is incorrect because ensuring peer code review is a best practice for code quality, but it is not the primary purpose of a security policy.

Option B is incorrect because push protection for secrets is managed through repository settings, not the security policy.

Option D is incorrect because customizing Dependabot configuration is related to dependency management, not directly to security policies.