$A$ and $B$ respectively are:
$A \xrightarrow[(2) Zn-H_2O]{(1) O_3} \text{Ethane-}1,2\text{-dicarbaldehyde} + \text{Glyoxal}$
$B \xrightarrow[(2) Zn-H_2O]{(1) O_3} 5\text{-oxohexanal}$

• A
  $1\text{-methylcyclohex-}1,3\text{-diene and cyclopentene}$
• B
  $\text{Cyclohex-}1,3\text{-diene and cyclopentene}$
• C
  $1\text{-methylcyclohex-}1,4\text{-diene and } 1\text{-methylcyclopent-}1\text{-ene}$
• D
  $\text{Cyclohex-}1,3\text{-diene and } 1\text{-methylcyclopent-}1\text{-ene}$