The correct answer is option 3: Diamond. Diamond is an allotrope of carbon that possesses a rigid three-dimensional structure.
Option 1: Graphite is not the correct answer as graphite has a layered structure and is not rigid in a three-dimensional sense.
Option 2: Fullerene, also known as buckminsterfullerene, is a molecule composed of carbon atoms in the form of a hollow sphere or ellipsoid. It does not have a rigid three-dimensional structure like diamond.
Option 4: Carbon black is a form of amorphous carbon that consists of small particles and does not have a well-defined rigid structure like diamond.
Therefore, the correct answer is diamond as it is the only allotrope of carbon that has a rigid three-dimensional structure.