The lower stability of ethyl anion compared to methyl anion and the higher stability of ethyl radical compared to methyl radical,respectively,are due to

• A
  $+I$-effect of the methyl group in ethyl anion; $\sigma \rightarrow p$-orbital conjugation in ethyl radical
• B
  $-I$-effect of the methyl group in ethyl anion and $\sigma \rightarrow \sigma^*$ conjugation in ethyl radical
• C
  $+I$ effect of the methyl group in both cases
• D
  $+I$-effect of the methyl group in ethyl anion and $\sigma \rightarrow \sigma^*$ conjugation in ethyl radical