If the sight distance (S) is equal to the length of the vertical-curve (2l) joining two grades g1% and - g2%, the height of the apex will be

• A. <img src="/_files/images/civil-engineering/surveying/65-3.211-1.png">
• B. <img src="/_files/images/civil-engineering/surveying/65-3.211-2.png">
• C. <img src="/_files/images/civil-engineering/surveying/65-3.211-3.png">
• D. none of these.