The barrier for rotation about indicated bonds will be maximum in which of these compounds?

The barrier for rotation about the indicated bonds Will be maximum in which of these three compounds ?

Carbon-carbon double bond length will be maximum in which of the following compounds ?

Carbon-carbon double bond lenghth will be maximum in which of the following compounds ?

Pick out the correct statements about the barrier of rotation about the indicated bond in the given compounds

The bond length of the S-O bond is maximum in which of the following compounds?

The bond length of the S-O bond is maximum in which of the following compounds?

Ordinarily the barrier to rotation about a carbon - carbon double bond is quite high but in compound P double bond between two rings was observed by NMR to have a rotational energy barrier of only about 20 cal/mol., showing that it has lot of single bond character. The reason for this is