Question A broken exhaust system can: Answers Let poisonous fumes into the cab. Improve fuel efficiency. Make steering more difficult. Explanation Defects in an exhaust system are very dangerous because they can cause poisonous fumes to enter the cab or sleeper berth. This questions appears in the following tests: Arizona Class B Knowledge Test Maryland Double Minnesota Bus Minnesota HazMat Missouri Class A Knowledge Test Missouri Class B Knowledge Test Missouri Passenger Nebraska Tank New Mexico Tank Oklahoma Passenger Oregon Class A Knowledge Test Virginia Double