Final answer:
The written report completed after discovering a defect or deficiency during a post-trip inspection is known as the Driver Vehicle Inspection Report (DVIR), which is option D.
Step-by-step explanation:
If you discover a defect or deficiency during your post-trip inspection as a commercial vehicle driver, you are required to complete a written report. This report is commonly referred to as a Driver Vehicle Inspection Report (DVIR). Option D is the correct answer. The DVIR is utilized to document any problems or issues found on the vehicle that could potentially affect its safety and operational capabilities. The report is then used by mechanics to make necessary repairs before the vehicle is used again. It's also important for record-keeping and compliance with transportation regulations that aim to ensure safety on the roads.