A) Generally solids are better conductors than liquids
B) Liquids are better conductors than gases
C) Metals are much better conductors than non-metals

Solids have molecules closely placed that helps in heat conduction.

In solids , atoms are close to each other than in liquids and gases. Hence in solids atoms transfer heat easily from one atom to another. In liquids also, atoms are closer but not as close in solids. This is why solids and liquids are better conductors of heat than gases.

Metals have free electrons which can move from atom to atom easily, whereas non-metals do not, their electrons are 'bound', meaning they cannot move easily. That's why metal are usually good conductors than non-metals.