The polar modulus for a solid shaft of diameter (D) is

• A. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-283-1.png">
• B. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-277-1.png">
• C. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-277-2.png">
• D. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-277-4.png">