Two molecules of hydrogen add on ‘A’ this shows that ‘A’ is either an alkadiene or an alkyne.
On reductive ozonolysis ‘A’ gives three fragments, one of which is dialdehyde. Hence, the molecule has broken down at two sites. Therefore, ‘A’ has two double bonds. It gives the following three fragments :
OHC—CH2—CH2—CHO, CH3CHO and CH3—CO—CH3
Hence, its structure as deduced from the three fragments must be