In the following sequence of reactions, $CH_3CH_2OH \xrightarrow{P + I_2} A \xrightarrow[\text{ether }]{\text{Mg}} B \xrightarrow{HCHO} C \xrightarrow{H_2O} D$ the compound 'D' is :

Question

( A ) n-propyl alcohol
( B ) n-butyl alcohol
( C ) propanal
( D ) butanal