The correct answer is option 3: graphite is a better electrical conductor than diamond.

Option 1 is incorrect: graphite is not harder than diamond. In fact, diamond is the hardest known substance, while graphite is a relatively soft material.

Option 2 is not directly related to the electrical conductivity of graphite. It is true that graphite and diamond are both forms of carbon, but their atomic structures are different, resulting in different physical properties. Graphite is made up of layers of carbon atoms arranged in a hexagonal lattice, allowing for the easy movement of electrons between the layers, making it a good electrical conductor. Diamond, on the other hand, has a tightly bonded network of carbon atoms, which does not allow for the same easy movement of electrons.

Option 4 is also incorrect: graphite does not have equal carbon-to-carbon distances in all directions. Its layered structure gives it a unique arrangement of carbon atoms, with strong bonds within the layers but weak interlayer forces. This results in the ability of the layers to slide over one another, giving graphite its characteristic slippery feel.