The ratio of the radius and apex distance of a curve deflecting through , is

• A. <img src="/_files/images/civil-engineering/surveying/71-3.290-1.png">
• B. <img src="/_files/images/civil-engineering/surveying/71-3.290-2.png">
• C. <img src="/_files/images/civil-engineering/surveying/71-3.290-3.png">
• D. <img src="/_files/images/civil-engineering/surveying/71-3.290-4.png">