(N/A) The stability of resonance structures is determined by several factors,including the number of covalent bonds,charge separation,and the electronegativity of atoms bearing charges.
$(a)$ Structure $(II)$ is less stable because it involves charge separation,whereas structure $(I)$ is a neutral molecule.
$(b)$ Structure $(I)$ is less stable because it has charge separation,while structure $(II)$ is a neutral molecule.
$(c)$ Structures $(I)$ and $(II)$ are equally stable because they are equivalent resonance structures (both are carboxylate ions).
$(d)$ Structure $(I)$ is less stable because it has charge separation,while structure $(II)$ is a neutral benzene molecule.
$(e)$ Structure $(II)$ is less stable because it involves charge separation,whereas structure $(I)$ is a neutral molecule.