I need help with these questions.

9. When does stress reversal in a ductile material result in hysteresis loops in a true stress-true strain curve? A. If the material only deforms elastically B. Hysteresis doesn't occur in ductile materials. C. If the material deforms plastically D. When cracks propagate in the material 10. A shaft has a modulus of rigidity of 158MPa, length of 1m, and polar second moment of area of 0.0001m4. If the torque on the shaft is 6,000N, what's the angular deflection? A. 0.776rad B. 0.426rad C. 0.137rad D. 0.380rad 11. Which of the following is involved in determining the midrange shear stress in a shaft? A. The midrange bending moment B. The torque amplitude C. The midrange torque D. The fatigue stress concentration factor for torsion