The ratio of the moments of resistance of a solid circular shaft of diameter D and a hollow shaft (external diameter D and internal diameter d), is

• A. <img src="/_files/images/civil-engineering/strength-of-materials/133-6.146-1.png">
• B. <img src="/_files/images/civil-engineering/strength-of-materials/133-6.146-2.png">
• C. <img src="/_files/images/civil-engineering/strength-of-materials/133-6.146-3.png">
• D. <img src="/_files/images/civil-engineering/strength-of-materials/133-6.146-4.png">
• E. none of these.