Orbital Overlap Involved in Hyperconjugation Effect

Hyperconjugation (often referred to as the Baker–Nathan effect or "no-bond resonance") is a stabilizing interaction that involves the delocalization of electrons from a $\sigma$ bond (most commonly a $\text{C}-\text{H}$ or $\text{C}-\text{C}$ $\sigma$ bond) into an adjacent empty, partially filled, or antibonding orbital.

In the case of a carbocation or a free radical:

• The adjacent $\text{sp}^3$ hybridized carbon has a bonding $\sigma$ orbital (such as the $\text{C}-\text{H}$ $\sigma$ orbital).
• The electron-deficient carbon possesses an empty or singly occupied unhybridized $p$-orbital.
• The stabilizing interaction occurs through the lateral overlap of the filled $\sigma$ orbital of the $\text{C}-\text{H}$ bond with this adjacent empty or half-filled $p$-orbital.

Thus, hyperconjugation fundamentally involves the overlap of a $\sigma$ orbital and a $p$ orbital ($\sigma - p$ overlap).

Therefore, the correct option is B.