A student compares the structures and conductivities of three carbon allotropes. In a solid, electrical current requires mobile charged particles, whereas thermal energy can be transferred by mobile electrons or by vibrations transmitted through a bonded lattice.

Allotrope	Simplified bonding model	Electrical conductivity	Thermal conductivity
Diamond	Each \(\text{C}\) atom forms \(4\) localized \(\sigma\) bonds in a continuous network.	Very low	High throughout the crystal
Graphene	Each \(\text{C}\) atom forms \(3\) localized \(\sigma\) bonds in a planar sheet, and the remaining valence electrons form a delocalized \(\pi\) system within the sheet.	High along the sheet	High along the sheet
Graphite	Graphene-like sheets are stacked with weak attractions between sheets; the \(\pi\) electrons are delocalized primarily within each sheet.	High parallel to the sheets and much lower perpendicular to the sheets	High parallel to the sheets and lower perpendicular to the sheets

Which of the following statements best accounts for the conductivity data?