Q is the discharge from an unconfined tube well with depression head S through a pipe of radius rw. If the radius of influence is R, the minimum required length of the strainer, is

• A. <img src="/_files/images/civil-engineering/water-supply-engineering/208-10.84-1.png">
• B. <img src="/_files/images/civil-engineering/water-supply-engineering/208-10.84-2.png">
• C. <img src="/_files/images/civil-engineering/water-supply-engineering/208-10.84-3.png">
• D. <img src="/_files/images/civil-engineering/water-supply-engineering/208-10.84-4.png">