Which of the following is the correct torsion equation?

• A. <img src="/_files/images/mechanical-engineering/strength-of-materials/101-202-1.png">
• B. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-279-1.png">
• C. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-279-2.png">
• D. <img src="/_files/images/mechanical-engineering/strength-of-materials/109-279-3.png">