The correct answer is option 4. This means that the statement "Graphite layers are held together by carbon-carbon single bond" is not correct.

To understand why option 4 is incorrect, let`s analyze the other options first:

Option 1 states that all carbons in diamond are linked by carbon-carbon single bonds. This is correct because diamond is a crystalline form of carbon, where each carbon atom is bonded to four surrounding carbon atoms through strong covalent bonds.

Option 2 states that graphite is a layered structure held together by weak van der Waals forces. This is also correct. Graphite is made up of multiple layers of carbon atoms arranged in a hexagonal pattern. These layers are held together by weak forces of attraction called van der Waals forces, which allow the layers to slide over each other easily and give graphite its characteristic properties.

Option 3 states that graphite layers are formed by hexagonal rings of carbon atoms. This is correct as well. The carbon atoms in graphite are arranged in hexagonal rings, and these rings stack on top of each other to form the layers.

Therefore, option 4 is incorrect because graphite layers are not held together by carbon-carbon single bonds. Instead, they are held together by the weaker van der