Identifying the Unidentified

Ammonia is a decently strong base. It would abstract a proton primarily. Ozonolysis in the next step indicates that elimination should've occurred in A.

Yeah, but if there's a st. chain, NH₃ replaces Br 2 give an amine lyke -

RCH₂Br ----(NH₃)---> RCH₂NH₂
Then why/how wud it deprotonate here ?

& wat does BaO do ?

it's simple. A is cyclohexene, then ozonolysis gives: succinic acid. Then BaO gives Pyrolysis reaction .. and hence cyclopentanone.
I'm 110% sure of my answer. :)

Yeah rite... Pyrolysis reaction !! (Is it a part which is taught under Carboxylic acids?)....

n how is this Cyclohexene being formed ?

Haan pyrolysis of esters and carboxylic acids is the topic.
Cyclohexene is formed by simple E2 elimination. The substrate is secondary, and elimination will be favoured for secondary substrates when a strong base attacks. If the base would have been weak/stabilised, substitution would've occurred.

NH3's nucleophile character is dominant in case you encounter with Primary halides and that's why favors substitution, while with cyclic / secendary and tert halides / groups, it's base character is dominant and favors elimination.
And.. about pyrolysis, I read it in Carbonyl.. and yeah it was in carboxylic acid too.

So am yet to study Pyrolysis......thnx all.. :)

yes arshad...adipic acid will b formed