Compare carbon-carbon bond rotation across A,B and C

The carbon-carbon bonds in benzene are

A new carbon-carbon bond is formed in

A new carbon-carbon bond is formed in

A new carbon-carbon bond is formed in

A new carbon - carbon bond formation is possible in :

Compare carbon -carbon bond lengths and bond energies by taking ethane, ethylene and acetylene as examples.

Compare carbon-carbon bond lengths and bond energies by taking ethane, ethylene and acetylene as examples.

Carbon-carbon bond length is same in

The carbon-carbon bond length is shortest in :