A)    Oxygen

B)    Nitrogen

C)    Phosphorous

D)    Carbon

Correct Answer: Option D - Carbon

Organic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds that contain carbon. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon and sulfur.

Because of their unique properties, multi-carbon compounds exhibit extremely large variety and the range of application of organic compounds is enormous. They form the basis of, or are important constituents of many products (paints, plastics, food, explosives, drugs, petrochemicals, to name but a few) and they form the basis of all earthly life processes.

Hence, options A, B and C are incorrect.