The standard equation of a cubical spiral transition curve provided on roads, is

• A. <img src="/_files/images/civil-engineering/highway-engineering/32-16-102-1.png">
• B. <img src="/_files/images/civil-engineering/highway-engineering/32-16-102-2.png">
• C. <img src="/_files/images/civil-engineering/highway-engineering/32-16-102-3.png">
• D. <img src="/_files/images/civil-engineering/highway-engineering/32-16-102-4.png">
• E. none of these.