The potential energy of a particle moving along the x-axis is V(x)=V0+21kx2, where k>0 and V0 is a constant. Which statement about the force on the particle and the nature of equilibrium at x=0 is correct?
a) Force is zero at x=0 and the equilibrium is neutral.
b) Force is non-zero at x=0 and the equilibrium is unstable.
c) Force is zero at x=0 and the equilibrium is stable.
d) Force is zero at x=0 and the equilibrium is unstable.