Which of the following is a non-metal which is a good conductor of electricity?

The periodic table has many distinct types of elements that are broken down into many categories. Metals, non-metals, and metalloids are the three different categories of elements that are known to exist. Metalloids are found between the non-metals on the periodic table's right side and the metals on its left, which are arranged in that order.

Graphite is a conductive non-metal. 

This crystalline carbon has a  planar layered structure. Graphene is a term used to describe each layer of the same layer. 

Conducting electricity is one of the main features of the elements, which is one of several properties that make the element useful. Free electrons are necessary for an element to carry electricity.
Graphite is a non-metal that may conduct electricity because it is the allotropic form of the carbon atom, a member of group 14 and a non-metal. We are aware that the carbon atom has four valence electrons; in the graphite form, three of these electrons participate in the production of the graphite's layers, while the fourth electron is free and capable of conducting electricity.

Graphite becomes conductive because the fourth electron has the opportunity to move to a  plane. The layers of carbon crystals were able to move quickly from each other because the weak van der Waals bonds hold them together so that the layers can be easily separated.

Hence, option A is correct.