What is the next step in the troubleshooting methodology after identifying the problem?

Establish a theory of probable cause.

The next step is to establish a theory of probable cause. The steps in the methodology are 1. Identify the problem, 2. Establish a theory of probable cause (Answer C), 3. Test the theory to determine cause (Answer A), 4. Establish a plan of action to resolve the problem and identify potential effects, 5. Implement the solution or escalate as necessary (Answer B), 6. Verify full system functionality and if applicable implement preventative measures, and 7. Document findings, actions, and outcomes (Answer D).