The correct answer is Question the user because the first step in the CompTIA Network+ (N10-009) troubleshooting methodology is to identify the problem. Identifying the problem involves gathering information, asking clarifying questions, determining if anything has changed, and establishing the scope of the issue.
Even though the user states they have "checked everything," the administrator should not assume that all relevant troubleshooting steps were properly performed. The technician must ask specific questions such as:
Are other users affected? Is the issue limited to certain websites? Are there any error messages? When did the issue start? Were there recent updates or configuration changes?
Only after gathering sufficient information should the administrator move to the next steps, such as establishing a theory of probable cause (Option B) or using divide-and-conquer methods (Option A).
Documentation (Option D) occurs after resolving and verifying the issue.
Therefore, questioning the user to clearly define and scope the problem is the correct first action according to the structured troubleshooting process.