professional vehicle inspections must be completed at least every three months. six months. year. two years…

Answer:

C. year.

Brief Explanations:

The question asks about the frequency of professional vehicle inspections. While specific requirements can vary by region, a common standard in many places (e.g., some U.S. states, European countries) is an annual inspection to ensure vehicle safety and compliance with regulations. This makes "year" the most probable correct answer among the options.