For having central angle , the area of cross-section of sewers running partially full, is

• A. <img src="/_files/images/civil-engineering/waste-water-engineering/182-9.50-1.png">
• B. <img src="/_files/images/civil-engineering/waste-water-engineering/182-9.50-2.png">
• C. <img src="/_files/images/civil-engineering/waste-water-engineering/182-9.50-3.png">
• D. <img src="/_files/images/civil-engineering/waste-water-engineering/182-9.50-4.png">