The correct answer is A. Carbon.
Organic compounds are compounds that contain carbon. They are found in all living things, and they are also used in many products that we use every day, such as plastics, medicines, and fuels.
Carbon is a very special element because it can form four bonds with other atoms. This makes it possible for carbon to form a wide variety of compounds, with different properties.
Nitrogen, sulfur, and potassium are also important elements, but they are not always present in organic compounds. For example, nitrogen is not present in methane (CH4), which is the simplest organic compound.
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