The correct option is Air.
Explanation
Matter is classified into pure substances and mixtures. Mixtures are further categorized as homogeneous or heterogeneous based on the uniformity of their composition. A homogeneous mixture has a uniform composition and properties throughout its mass, meaning the individual components are not distinguishable by the naked eye.
Option Analysis:
- Air (Correct): Air is a homogeneous mixture of gases. It consists primarily of nitrogen (~78%) and oxygen (~21%), along with argon, carbon dioxide, and trace amounts of other gases. These components are mixed uniformly at the molecular level, making the mixture consistent throughout a given sample.
- Soil (Incorrect): Soil is a heterogeneous mixture. It contains distinct particles of sand, clay, organic matter, pebbles, and air pockets. The composition is not uniform and varies visibly within a sample.
- Granite (Incorrect): Granite is a heterogeneous mixture of minerals, typically quartz, feldspar, and mica. The individual mineral grains are clearly visible and distinct from one another.
- Sand (Incorrect): Sand is a heterogeneous mixture composed of small grains of various rocks and minerals. The particles vary in size, shape, and composition.
Key Takeaway:
Air is a classic example of a homogeneous mixture (solution) in the gaseous state because its constituent gases are uniformly distributed. In contrast, soil, granite, and sand are heterogeneous mixtures with non-uniform compositions.