The CompTIA Troubleshooting Methodology states that after testing the theory, the next step is to establish a plan of action to resolve the issue. Troubleshooting Steps: Identify the problem. Establish a theory of probable cause. Test the theory to determine the cause. Establish a plan of action and implement the solution. # (Correct step) Verify full system functionality. Document findings, actions, and outcomes. Breakdown of Options: A: Verify full system functionality - Happens after implementing the solution. B: Document the findings and outcomes - Final step, happens after resolving the issue. C: Establish a plan of action - # Correct answer. Comes immediately after confirming the cause. D: Identify the problem - First step, already completed. Reference: CompTIA Network+ (N10-009) Official Study Guide - Domain 5.1: Explain network troubleshooting methodology.