NOTES

A elemental analysis gives C₃H₈O₂, IR shows -OH, 13C implies symmetry
A to B = oxidation of primary alcohol to carboxylic acid
B to C = esterification, ethyl ester obtained - nmr indicates symmetrical diethyl ester
D C5H8 IHD = 2, IR suggests C=C and 13 C shows 4 sp2C so it looks like a diene.
D to E = conjugate addition of bromine to give the dibromide.
E to F = reduction of alkene to alkane
C + F to G = form enolate of active methylene and double alkylation with dibromide F.
G to 3-methylcyclopentanecarboxylic acid = ester hydrolysis and decarboxylation (gas lost is CO2)

Mechanism : 1,4-conjugate addition of Br2 to a conjugated diene.

KEY steps.... You should be able to work out A and D from the data provided about each of these compounds.