The pair of resonanating structures among the following is:

The number of $\mathrm{\pi }$ electrons required for a planar cyclic conjugated system to exhibit aromatic behaviour is $(4\mathrm{n}+2).$ Here $\mathrm{n}$ is:

Following is an example of:

The relative stabilites of the following carbocations is:

Which of the following represents the true order of bond dissociation energy of the indicated $\mathrm{C}-\mathrm{H}$ bond of the following molecules?

The most carbocations, carbanions, free radicals and radical cations are reactive carbon intermediates.

Their hybrid orbitals respectively are: