Final answer:
The minimum clearance heights for electrical service drop lines are 12 feet above the road, 15 feet above driveways or walkways, and 18 feet above flat roofs, corresponding to option b.
Step-by-step explanation:
The question relates to the minimum clearance heights for electrical service drop lines above different types of surfaces. A drop line must be 12 feet above the road, 15 feet above driveway or walkway, and 18 feet above a flat roof. By considering the various heights mentioned in increments of one foot, such as a line of one foot, two feet, and so on, up to eight feet, it is determined that the drop line heights need to be in larger increments to ensure safety and compliance with standards. Hence, the correct answer to the question is option b: 12 feet, 15 feet, 18 feet.