In the following sequence of reactions,the alkene affords the compound $B$.
$CH_3-CH=CH-CH_3$ $\xrightarrow{O_3} A$ $\xrightarrow[Zn]{H_2O} B$
The compound $B$ is:

• A
  $CH_3CH_2CHO$
• B
  $CH_3COCH_3$
• C
  $CH_3CH_2COCH_3$
• D
  $CH_3CHO$