$P \underset{2.H_3O^+}{\xrightarrow{\;\;1.CH_3MgBr\;\;}} R \underset{\triangle}{\xrightarrow{\;\;1.dil.NaOH\;\;}}\text{4–methylpent–3–en–2–one}$
P is
propanone
ethanamine
ethanenitrile
ethanal
$P \underset{2.H_3O^+}{\xrightarrow{\;\;1.CH_3MgBr\;\;}} R \underset{\triangle}{\xrightarrow{\;\;1.dil.NaOH\;\;}}\text{4–methylpent–3–en–2–one}$
P is