Texas CDL General Knowledge Practice Exam

The correct choice indicates that 4-way flashers cannot be checked simultaneously with the other lights. When 4-way flashers are activated, they cause all four turn signals to flash at once, which is a distinct function from headlights, brake lights, and individual turn signals. This means that while 4-way flashers are on, you cannot independently check the functioning of just the turn signals, brake lights, or headlights, as they would all be affected by the activation of the 4-way flashers. In contrast, headlights can be checked without interfering with the operation of turn signals, brake lights, or 4-way flashers because they operate independently. Similarly, brake lights illuminate when the brake pedal is pressed, allowing for clear checking without interference from the other light functions. Therefore, 4-way flashers stand out as the option that disrupts the ability to check the other lights at the same time.