* Solids: Conduction is most efficient in solids because the particles are tightly packed, allowing for easy transfer of heat energy through vibrations.

* Liquids: Conduction occurs in liquids, but it is less efficient than in solids because the particles are more spread out and move more freely.

* Gases: Conduction happens in gases, but it is the least efficient because the particles are very far apart and move very quickly, making it difficult for them to transfer heat energy.

Therefore, conduction can occur in solids, liquids, and gases.