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

• A. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/10-48-1.png">
• B. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/10-48-2.png">
• C. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/10-48-3.png">
• D. <img src="/_files/images/civil-engineering/upsc-civil-service-exam-questions/10-48-4.png">