The horizontal surface is a level plane at what elevation?

• A. 150 ft
• B. 100 ft
• C. 200 ft
• D. 250 ft

Answer: (A)

A horizontal surface is a level plane, meaning it has no slope and is perpendicular to gravity. Every point on that plane shares the same elevation relative to the reference datum. In the diagram, the horizontal line crosses the vertical scale exactly at the 150 ft mark, so the whole surface lies at 150 ft elevation. The other numbers would correspond to different heights, but they don’t match the level line shown.