The hyperconjugative stabilities of tert-butyl cation and $2-$butene,respectively,are due to

• A
  $\sigma \rightarrow p$ (empty) and $\sigma \rightarrow \pi^{\star}$ electron delocalisations.
• B
  $\sigma \rightarrow \sigma^{\star}$ and $\sigma \rightarrow \pi$ electron delocalisations.
• C
  $\sigma \rightarrow p$ (filled) and $\sigma \rightarrow \pi$ electron delocalisations.
• D
  $p$ (filled) $\rightarrow \sigma^{\star}$ and $\sigma \rightarrow \pi^{\star}$ electron delocalisations.