Two monomers in maltose are :

Arrange the following bonds according to their average bond energies in descending order :
C–Cl, C–Br, C–F, C–I

A metal (A) on heating in nitrogen gas gives compound B. B on treatment with H₂O gives a colourless gas which when passed through CuSO₄ solution gives a dark blue-violet coloured solution. A and B respectively, are :

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