Which of the following is not a homogeneous mixture.

Options

A. Air
B. Brass
C. Solution of sugar in wate
D. Smoke

Explanation

To determine which of the following is not a homogeneous mixture, we need to understand the definition of a homogeneous mixture. A homogeneous mixture is one in which the components are uniformly distributed and only one phase is visible throughout the mixture.

### Step-by-Step Solution:

1. **Understand Homogeneous Mixtures**:
- A homogeneous mixture is defined as a mixture where the components are uniformly mixed, resulting in a single phase that is consistent throughout. Examples include air, sugar dissolved in water, and alloys.

2. **Analyze the Options**:
- We need to evaluate each option provided to identify which one does not fit the definition of a homogeneous mixture.

3. **Evaluate Each Option**:
- **Option 1: Air**: Air is a mixture of gases (mainly nitrogen and oxygen) that are uniformly distributed. Thus, it is a homogeneous mixture.
- **Option 2: Brass**: Brass is an alloy made of copper and zinc. The composition is uniform throughout, making it a homogeneous mixture.
- **Option 3: Sugar solution in water**: When sugar is dissolved in water, it forms a clear solution where the sugar is uniformly distributed. Therefore, it is a homogeneous mixture.
- **Option 4: Smoke**: Smoke consists of solid particles suspended in a gas (air). The composition of smoke is not uniform, as it contains varying amounts of particles and gases. This makes smoke a heterogeneous mixture.

4. **Conclusion**:
- Based on the evaluations, the option that is not a homogeneous mixture is **smoke**.

### Final Answer:
**Smoke is not a homogeneous mixture.**

---