Question Mirror adjustment can only be checked properly if: Answers The trailer is straight. There is no trailer. The vehicle is on a slight incline. Explanation On a vehicle with one or more trailers, mirror adjustment can only be checked accurately if the trailers are straight. Mirror adjustment should be checked before the start of every trip. Take a FREE Practice Test Now This questions appears in the following tests: New Mexico Knowledge Test Class A , Washington Knowledge Test Class A , Louisiana Knowledge Test Class B , Rhode Island Knowledge Test Class B , Arizona Passenger , Ohio Passenger ,