The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock's law, is

• A. <img src="/_files/images/civil-engineering/waste-water-engineering/190-9.161-1.png">
• B. <img src="/_files/images/civil-engineering/waste-water-engineering/190-9.161-2.png">
• C. <img src="/_files/images/civil-engineering/waste-water-engineering/190-9.161-3.png">
• D. <img src="/_files/images/civil-engineering/waste-water-engineering/190-9.161-4.png">