Which statement about organic molecules is true?

• A. They consist of carbon and hydrogen
• B. They are always liquids
• C. They are always large
• D. They cannot form polymers

Answer: (A)

Organic molecules are defined by containing carbon atoms bonded to other elements, most commonly hydrogen. That carbon–hydrogen framework is the hallmark of organic chemistry and underlies the vast diversity of organic compounds, from simple gases like methane to large macromolecules such as proteins, carbohydrates, and DNA. Because of this carbon-and-hydrogen basis, the statement that organic molecules consist of carbon and hydrogen is true.

They’re not restricted to a single physical state. Organic compounds can be gases (methane), liquids (ethanol), or solids (wax). So being always a liquid is not correct.

Size also varies. There are many small organic molecules, not just large ones, so they aren’t always large.

And yes, organic molecules can form polymers. Many important polymers—like starch, proteins, and DNA—are made from repeating organic units linked together.

So the most accurate feature is that organic molecules consist of carbon and hydrogen.