The correct option is B Contributing structures contribute to the resonance hybrid in proportion of their energies.
Individual Lewis structures of a resonance hybrid are hypothetical
mental constructs, and the molecular geometry and properties implied by
each structure standing alone do not correspond to any real chemical
species. To correctly interpret the molecular structure described by a
resonance hybrid, all significant contributors of the resonance hybrid
must be considered together, since the hybrid represents the actual
molecule as their "average", with bond lengths and other structural
parameters taking on intermediate values compared to those expected for
the individual Lewis structures of the contributors, were they to exist
as "real" chemical entities.
The contributing structures differ only in the formal
apportionment of electrons to the atoms, and not in the actual
physically and chemically significant electron or spin density. While
contributing structures will differ in formal bond orders and, possibly,
in formal charge assignments,the contributing structures of a resonance hybrid all represent a single chemical species.
In particular, each contributing structure represents the same
molecular geometry (position of atomic nuclei) and electron/spin
distribution.
Because electron delocalization lowers the potential energy of a
system, any species represented by a resonance hybrid is more stable
than any of the (hypothetical) contributing structures. The difference
in potential energy between the actual species and the (computed) energy
of the contributing structure with the lowest potential energy is
called the resonance energy or delocalization.
conclusion; hence the option (A) is not true.