Question

what 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 all organic molecules, which are defined by containing carbon as a core structural element. Nitrogen is not present in most carbohydrates or lipids; ammonia is a compound, not an element; legumes are a type of plant, not an element.

Answer:

carbon