Stress and strain — practice question

For a wire, Hooke’s law is obeyed for a tension $F$ and extension $x$. The Young modulus for the material of the wire is $E$. Which expression gives the elastic potential energy stored in the wire?

• A$\tfrac{1}{2}Ex$
• B$Ex$
• C$\tfrac{1}{2}Fx$
• D$Fx$