Question Mirror adjustment can only be checked properly if: Answers The trailer is straight. There is no trailer attached to the tractor. The vehicle is on a slight incline. The vehicle is on a slight decline. Explanation If a trailer is attached to a tractor, the adjustment of the vehicle's mirrors can only be checked accurately if the trailer is straight. Take a FREE Practice Test Now This questions appears in the following tests: Montana Knowledge Test Class A , Georgia Knowledge Test Class B , Kansas Bus , North Dakota Double ,