Question

which is a key element found in all carbohydrates, lipids, proteins, and nucleic acids?
nitrogen
ammonia
carbon
legumes

Explanation:

Carbohydrates, lipids, proteins, and nucleic acids are the four main biological macromolecules. Nitrogen is absent in most lipids; ammonia is a compound, not an element; legumes are a type of plant, not an element. Carbon forms the backbone of all these macromolecules, making it present in all four.

Answer:

carbon