Do you currently have car insurance? Yes I have insurance. Great, you're all set! Click here if you still want to compare rates. No, I need insurance and I want to compare options. Before you start the test, please answer the following question regarding your insurance status. Without insurance you will not be able to drive in California Question Poisonous fumes can enter the cab due to: Answers A defective exhaust system. The wrong type of fuel being used. A lack of oil in the engine. Under-inflated tires. Explanation Defects in an exhaust system are very dangerous because they can cause poisonous fumes to enter the cab or sleeper berth. Take a FREE Practice Test Now This questions appears in the following tests: Colorado Knowledge Test Class A , Massachusetts Knowledge Test Class A , Montana Knowledge Test Class A , North Carolina Knowledge Test Class B ,