Which label describes compounds in which carbon atoms are almost always bonded to each other, to hydrogen atoms, and a few other atoms (Oxygen, Nitrogen, Sulfur, Phosphorus)?

• A. Organic
• B. Inorganic
• C. Structural isomer
• D. Indicator

Answer: (A)

The label describes carbon-based molecules built around carbon–carbon bonds and carbon–hydrogen bonds, with other atoms like oxygen, nitrogen, sulfur, or phosphorus often attached as functional groups. This carbon-centered framework is the defining feature of organic compounds, which is why this label fits best. Organic chemistry focuses on how carbon chains and rings form a vast variety of substances, from methane to complex biomolecules, with hydrogen and a few heteroatoms decorating the carbon skeleton.

Inorganic would cover substances that don’t rely on carbon–hydrogen frameworks, such as salts or metals, though there are carbon-containing inorganic compounds, those aren’t the typical category implied here. A structural isomer is a way two compounds can have the same formula but different connectivity, not a broad label for the class of compounds. An indicator is simply a substance used to signal a condition, not a description of the type of compound.