Fatigue driving is one of the important causes of traffic accidents. Many truck drivers often drive more than 8 hours in a row. Therefore, traffic police set up inspection stations at some highway toll stations to check the fatigue status of truck drivers in order to reduce the fatigue of truck drivers. If the following options are true, which of the following is the most challenging question for the traffic police? ['It is difficult to have an exact evaluation and comparison index of human fatigue.', "The fatigue state of the truck driver's body is not necessarily a reflection of his continuous driving time.", 'Many truck drivers are unaware of the existence of this inspection before being inspected.', 'Some truck drivers will respond to traffic police inspections by driving at rest stations in advance.']