V and R are the regime mean velocity and hydraulic mean depth respectively in metres. Lacey's silt factor f is

• A. <img src="/_files/images/civil-engineering/irrigation/16-15-38-1.png">
• B. <img src="/_files/images/civil-engineering/irrigation/16-15-38-2.png">
• C. <img src="/_files/images/civil-engineering/irrigation/16-15-38-3.png">
• D. <img src="/_files/images/civil-engineering/irrigation/16-15-38-4.png">