An unsaturated molecule contains?

• A. At least one double bond
• B. Only single bonds
• C. No bonds
• D. Only triple bonds

Answer: (A)

Unsaturated molecules have fewer hydrogens than the corresponding saturated form because they contain multiple bonds that lock the carbon atoms together more tightly. In basic chemistry, this is most clearly signaled by a carbon–carbon double bond. When you spot at least one C=C bond, the molecule is considered unsaturated and can typically undergo addition reactions that would add more atoms across that double bond, increasing its hydrogen count. The other options describe situations that don’t fit this quick identification: a molecule with only single bonds is fully saturated, a molecule with no bonds isn’t a meaningful description here, and while a molecule with a triple bond is also unsaturated, the standard quick test taught at this level is the presence of a double bond.