The correct answer is C. charcoal.
Amorphous carbon is a form of carbon that does not have a regular crystal structure. It is often found in nature as charcoal, soot, and lampblack. Amorphous carbon is also produced industrially as a byproduct of the production of steel and other metals.
Diamond is a crystalline form of carbon that is characterized by its high hardness and its ability to reflect light. Graphite is another crystalline form of carbon that is characterized by its softness and its ability to conduct electricity. Fullerenes are a class of carbon molecules that have a cage-like structure.
Charcoal is a form of amorphous carbon that is produced by heating organic materials, such as wood, in the absence of oxygen. Charcoal is a black, porous solid that is used as a fuel, a pigment, and a filter.
Soot is a fine black powder that is produced by the incomplete combustion of carbon-containing materials. Soot is a major component of air pollution and is a health hazard.
Lampblack is a fine black powder that is produced by the incomplete combustion of hydrocarbons. Lampblack is used as a pigment and as a filler in rubber and plastics.