A. Establish a theory of probable cause
The 7 steps to troubleshooting are:
1. Identify the problem
2. Establish a theory of probable cause
3. Test the theory to determine the cause
4. Establish a plan of action to resolve the problem
5. Implement the solution
6. Verify full system functionality, and, if applicable, implement preventive measures
7. Document findings, actions and outcomes
I think the assumption is, because a user was having an issue the technician verified that the issue was valid, so they are merely identifying that there is a problem. We aren't told that we know what the issue is, so the next step is likely to Establish a theory of probable cause. Knowing that there is an issue and knowing/guessing why the issue exists is where we need to differentiate.