d
\(P{{h}_{3}}\overset{\centerdot }{\mathop{C}}\,\) is more stable than \({{\left( C{{H}_{3}} \right)}_{3}}\overset{\,\,\centerdot }{\mathop{C}}\,\) because resonance stabilisation effect in \(P{{h}_{3}}\overset{\centerdot }{\mathop{C}}\,\) is more pronounced as compared to hyperconjugation stabilisation effect in \({{\left( C{{H}_{3}} \right)}_{3}}\overset{\,\,\centerdot }{\mathop{C}}\,\) overall stability order among free radical is : Triphenylmethyl \(>\) benzyl \( >\) allyl \(>\) tertiary alkyl \(>\) secondary \(>\) primary \(>\) methyl \(>\) vinyl