Which statement is true of all organic compounds?

• A. They all contain a benzene ring.
• B. They all contain a ${\mathrm{COOH}}_1$ group.
• C. They all contain carbon atoms.
• D. They all contain nitrogen atoms.

Answer: (C)

Verified step by step guidance

1. Recall the definition of organic compounds: Organic compounds are primarily characterized by the presence of carbon atoms bonded to hydrogen, oxygen, nitrogen, or other elements.
2. Evaluate each statement: First, consider if all organic compounds contain a benzene ring. Benzene rings are specific aromatic structures, but many organic compounds do not have them (e.g., alkanes, alcohols).
3. Next, check if all organic compounds contain a \( COOH \) group (carboxylic acid group). This is not true because many organic compounds lack this functional group (e.g., alkanes, alkenes, alcohols).
4. Then, consider if all organic compounds contain nitrogen atoms. Nitrogen is present in some organic compounds (amines, amides), but many do not contain nitrogen (e.g., hydrocarbons).
5. Finally, confirm that all organic compounds contain carbon atoms, which is the defining feature of organic chemistry. Therefore, the statement 'They all contain carbon atoms' is true for all organic compounds.