Identify the interaction described

The question says:

interaction between a $\pi$ bond and a lone pair of electrons present on an adjacent atom

This is the classic condition for resonance (also called the mesomeric effect), where electron density is delocalized through overlap of adjacent $p$ orbitals.

Recall the definitions of the given effects

• Resonance effect: Delocalization of electrons due to interaction of

  • $\pi$ bond with $\pi$ bond, or
  • $\pi$ bond with lone pair, or
  • lone pair with positive charge/vacant orbital.

• Electromeric effect: Temporary complete transfer of a $\pi$ electron pair to one atom in presence of an attacking reagent.

• Hyperconjugation: Delocalization involving $\sigma$ bonds (usually $C-H$) adjacent to a multiple bond or carbocation.

• Inductive effect: Permanent polarization of $\sigma$ bonds due to electronegativity differences.

Match the description

Since the question specifically mentions interaction between a $\pi$ bond and a lone pair on an adjacent atom, this corresponds to resonance effect.

Check options

• A: Resonance effect $\rightarrow$ Correct
• B: Electromeric effect $\rightarrow$ Incorrect
• C: Hyperconjugation $\rightarrow$ Incorrect
• D: Inductive effect $\rightarrow$ Incorrect

Final answer

The correct option is A.