When k is denoted as the spring constant; s$,$ spring deformation from its unstretched state; v$,$ velocity of the particle or point on the rigid body attached to the spring end, elastic potential energy is defined as

$+(1/2)$ k $($s$)2$

$-(1/2)$ k $($s$)2$

$+(1/2)$ k $($v$)2$

None of the rest