Identify a compound among the following

Options

A. Common salt
B. Air
C. Sugar
D. Diamond.

Explanation

To identify a compound among the given options, we need to understand what a compound is. A compound is a substance formed when two or more different elements combine chemically in a fixed ratio. Let's analyze each option:

1. **Common Salt (Sodium Chloride - NaCl)**: This is a compound formed from sodium (Na) and chlorine (Cl) atoms. It is a chemical combination of these two elements.

2. **Air**: Air is a mixture of gases, primarily nitrogen and oxygen, along with other gases. It does not have a fixed composition and is not a compound.

3. **Sugar (Sucrose - C12H22O11)**: Sugar is a compound made up of carbon (C), hydrogen (H), and oxygen (O) atoms. These elements are chemically combined in a specific ratio.

4. **Diamond (Carbon - C)**: Diamond is an allotrope of carbon and consists solely of carbon atoms. It is an element, not a compound.

Now, based on this analysis, we can conclude that the compound among the options is:

**Answer: Sugar (C)**

### Step-by-Step Solution:
1. **Understand the definition of a compound**: A compound is formed when two or more different elements combine chemically.
2. **Analyze each option**:
- Common Salt: A compound (NaCl).
- Air: A mixture, not a compound.
- Sugar: A compound (C12H22O11).
- Diamond: An element (pure carbon).
3. **Identify the compound**: From the analysis, sugar is the only compound listed.