Which of the following is not required in the drainage system of highways?

• A. The highest level of the underground water table should be placed above the level of the sub-level
• B. The side drain should have sufficient capacity and longitudinal slope so that all the water collected on the surface can drain out.
• C. Surface water from the carriageway and shoulder must be drained efficiently as it does not allow subgrade
• D. Special care should be taken in aqueous areas, especially when it contains harmful salts.