Which of the following functional groups contains a carbon atom double-bonded to an oxygen atom ($C=O$)?

• A. Carbonyl group
• B. Sulfhydryl group
• C. Amino group
• D. Hydroxyl group

Answer: (A)

Verified step by step guidance

1. Identify the functional groups listed in the problem: Carbonyl group, Sulfhydryl group, Amino group, and Hydroxyl group.
2. Understand the structure of each functional group: A Carbonyl group contains a carbon atom double-bonded to an oxygen atom, represented as $C=O$.
3. Recognize that the Sulfhydryl group contains a sulfur atom bonded to a hydrogen atom, represented as $S-H$.
4. Note that the Amino group consists of a nitrogen atom bonded to hydrogen atoms, typically represented as $\mathrm{NH}$₂.
5. Understand that the Hydroxyl group contains an oxygen atom bonded to a hydrogen atom, represented as $\mathrm{OH}$.