Final answer:
Trina logging in for Doug using her credentials goes against the need-to-know principle, which restricts access to information only to those who need it to perform their job functions.
Step-by-step explanation:
If Trina logs in for Doug using her credentials, the access control principle that is violated is the need-to-know principle (C). This principle stipulates that access rights should be granted only to individuals who must have the information necessary to perform their duties. Sharing credentials allows Doug access to information that he might not be authorized to view, which violates this principle. The least privilege principle is about giving users the minimum levels of access - or permissions - they need to perform their job functions, but does not directly pertain to this situation. Separation of duties involves splitting responsibilities among multiple people to prevent fraud and errors, which is not directly addressed by sharing credentials. Lastly, Role-Based Access Control (RBAC) refers to assigning permissions based on roles within an organization, but the violation here is not regarding the permissions of roles, but the sharing of credentials that enable access outside of an individual's role.