Identify the overlapping orbitals involved in hyperconjugation from...

Hyperconjugation involves the delocalization of electrons by the overlapping of a filled $\sigma$ orbital (usually of a C-H or C-C bond) with an adjacent empty or partially filled $p$ orbital or a $\pi$ orbital.

Because it most commonly involves the interaction between a $\sigma$ bond and a $p$ orbital (such as in carbocations or free radicals), it is also known as $\sigma - p$ conjugation.

Therefore, the overlapping orbitals involved in hyperconjugation are $\sigma$ and $p$.

Answer: $\sigma - p$