The correct answer is: D. Four other carbon atoms
In a diamond, each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement. This means that each carbon atom is connected to four other carbon atoms by covalent bonds, which are strong bonds that form when atoms share electrons. The tetrahedral arrangement of the carbon atoms gives diamond its strength and hardness.
Option A is incorrect because each carbon atom is bonded to four other carbon atoms, not five.
Option B is incorrect because each carbon atom is bonded to four other carbon atoms, not three.
Option C is incorrect because each carbon atom is bonded to four other carbon atoms, not two.