Final answer:
The right side of the road is marked by a solid white line, which serves as a boundary to guide drivers and maintain proper lane discipline. The correct answer is option D.
Step-by-step explanation:
The line used to mark the right side of the road is D. solid white. On roads, color and pattern of lane lines convey important information about lane usage and road rules. A solid white line is generally used to indicate the right edge of the roadway or the boundary between a travel lane and a shoulder.
In contrast, broken lines (whether white or yellow) indicate where vehicles may cross to change lanes or pass, while solid yellow lines define separation of traffic moving in opposite directions. Therefore, for marking the right side, a solid white line is used to guide drivers and maintain proper lane discipline.