A foreign airline manager: "Although the newly developed collision avoidance system has not been thoroughly tested to find potential problems, it must also be installed on the passenger plane immediately because the system's mechanical alarm device can prevent pilots from crashing. "The company's pilots:" Pilots cannot fly an aircraft that has not been fully tested for collision avoidance systems because a malfunctioning collision avoidance system will mislead the pilot and cause a collision. ". Which of the following best reinforces pilot opposition? ['Mechanical equipment is always at risk.', 'The jet engine was not thoroughly tested before it was first put into service, but its performance and safety record is obvious.', 'Although the collision avoidance system allows pilots to avoid some collision accidents, the potential problems of untested collision avoidance systems may cause more crashes.', 'Many crashes are caused by pilot fatigue.']