The correct answer is: D. does not change the vertical alignment of road.
Superelevation is the banking of a road to counteract the centrifugal force experienced by vehicles traveling around a curve. It is achieved by rotating the pavement about the inner edge of the pavement. This does not change the vertical alignment of the road, which is the shape of the road’s surface as it rises and falls.
Option A is incorrect because superelevation is not preferable in steep terrain. In fact, it is often avoided in steep terrain because it can make the road more dangerous.
Option B is incorrect because superelevation does not result in balancing the earthwork. The earthwork is the material that is excavated or filled to create the roadbed. Superelevation does not affect the amount of earthwork that is required.
Option C is incorrect because superelevation does not avoid the drainage problem in flat terrain. Drainage is the process of removing water from the road surface. Superelevation does not affect the drainage of the road.