When placing a warning device on a two-lane road, how far should it be placed in front of the vehicle?

Answer: C — 100 feet

The correct distance to place a warning device in front of your vehicle on a two-lane road is 100 feet. This distance is significant because it provides adequate warning for approaching drivers, allowing them time to react and slow down. In situations where a vehicle is disabled or there has been an accident, the earlier a warning device is visible, the more effective it is in preventing further incidents. Placing the device 100 feet away ensures that drivers have enough time to observe the warning and take necessary actions, such as changing lanes or reducing speed, to navigate safely around the situation. The other options are either insufficient distances that do not provide enough warning time for other motorists or are excessive, which could lead to the warning device being overlooked and diminish its effectiveness.