The functional group in CH₃CHO is:

**Step‑by‑step solution** 1. Identify the compound: CH₃CHO (acetaldehyde) consists of a carbon chain with a –CHO terminal group. 2. The –CHO group is the aldehyde functional group, characterized by a carbonyl (C=O) attached to at least one hydrogen. 3. Examine each option: (a) Alcohol – contains an –OH group; CH₃CHO has no –OH. → fails. (b) Ketone – contains a carbonyl (C=O) in the middle of a chain; CH₃CHO has the carbonyl at the end. → fails. (c) Aldehyde – exactly matches the –CHO group present. → correct. (d) Ether – contains an –O– linkage between two carbons; CH₃CHO does not. → fails. 4. Therefore the functional group in CH₃CHO is an aldehyde. **Answer:** (c) Aldehyde