Correct statement by changing underline part of sentence
Aldehydes and ketones both contain a `ul("carboxyl group")`,

Explanation

To correct the statement "Aldehydes and ketones both contain a carboxyl group," we need to replace the underlined part with the correct functional group that characterizes both aldehydes and ketones.

### Step-by-Step Solution:

1. **Identify the Incorrect Part**: The statement incorrectly states that aldehydes and ketones contain a "carboxyl group." The carboxyl group (-COOH) is characteristic of carboxylic acids, not aldehydes or ketones.

2. **Understand the Functional Groups**:
- Aldehydes contain a carbonyl group (C=O) with at least one hydrogen atom attached to the carbon. The general structure is represented as RCHO, where R is a hydrocarbon group.
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