The ratio of the torsional moments of resistance of a solid circular shaft of diameter D, and a hollow circular shaft having external diameter D and internal diameter d is given by

• A. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/70-991-1.png">
• B. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/70-991-2.png">
• C. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/70-991-3.png">
• D. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/70-991-4.png">