If h1 is the height of the driver's eye and h2 is the height of an obstruction above road surface, then, for a minimum sight distance S, the length of the vertical curve should be greater than

• A. <img src="/_files/images/civil-engineering/highway-engineering/33-16-118-1.png">
• B. <img src="/_files/images/civil-engineering/highway-engineering/33-16-118-2.png">
• C. <img src="/_files/images/civil-engineering/highway-engineering/33-16-118-3.png">
• D. <img src="/_files/images/civil-engineering/highway-engineering/33-16-118-4.png">