The correct answer is A. Coal-tar.
Coal-tar is a thick, black liquid that is a byproduct of the process of making coke from coal. It is a complex mixture of hundreds of different chemicals, including naphthalene. Naphthalene is a white, crystalline solid that is used in a variety of products, including mothballs, insecticides, and synthetic rubber.
Diesel is a fuel oil that is used in diesel engines. It is a clear, colorless liquid that is made from petroleum. Diesel fuel is a complex mixture of hydrocarbons, which are compounds that are made up of hydrogen and carbon atoms.
Charcoal is a black, porous solid that is made from wood or other organic materials that have been heated to a high temperature. Charcoal is used in a variety of products, including barbecues, water filters, and activated charcoal.
Camphor is a white, crystalline solid that is extracted from the bark of the camphor tree. Camphor is used in a variety of products, including mothballs, liniments, and incense.
Coal-tar is the chief source of naphthalene because it is a byproduct of the process of making coke from coal. Naphthalene is a white, crystalline solid that is used in a variety of products, including mothballs, insecticides, and synthetic rubber.