On a hill, how far should a warning device be placed behind the vehicle?

Answer: C — 100-500 feet

The correct distance to place a warning device behind a vehicle on a hill is 100-500 feet. This range is important for ensuring safety, as it provides adequate warning to oncoming traffic about a potential hazard. When a vehicle is stationary on a hill, visibility may be limited, particularly for drivers who are approaching from behind or from below. Placing the warning device further away, within the 100-500 feet range, gives approaching drivers sufficient time to react and take necessary action, minimizing the risk of collisions. The distance ensures that the warning device is clearly visible while allowing vehicles to have enough stopping distance, taking into account the slope and potential speeds at which other vehicles may be traveling. This practice is particularly crucial in mountainous or hilly areas where drivers may not anticipate an obstacle ahead, as the incline can hinder their line of sight until they are relatively close.