Strain energy of a member may be equated to_____.

A)
average resistance x displacement
B)
1 / 2 stress x strain x area of its cross-section
C)
1 / 2 stress x strain x volume of the member
D)
1 / 2 (stress)² x volume of the member + Young's modulus E.

Correct Answer :   1 / 2 (stress)² x volume of the member + Young's modulus E.