In the following sequence of reactions the maximum number of atoms present in molecule 'C' in one plane is _________. (A is a lowest molecular weight alkyne)

The major product [B] in the following sequence of reactions is :-

Among the compounds A and B with molecular formula C₉H₁₈O₃ , A is having higher boiling point the B. The possible structures of A and B are :

An unsaturated hydrocarbon X absorbs two hydrogen molecules on catalytic hydrogenation and also gives following reaction : B(3 - oxo - hexanedicarboxylic acid) X will be :-