Usha took a lump of dry soil in a glass and added water to it till it was completely immersed. She observed bubbles coming out. The bubbles contain

Options

A. water vapour
B. only oxygen gas
C. air
D. none of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Experiment**: Usha took a lump of dry soil and added water to it until the soil was completely submerged. This means that the soil was in contact with water.

2. **Observation of Bubbles**: Usha observed bubbles coming out of the soil when it was submerged in water. This indicates that something is being released from the soil.

3. **Identifying the Source of Bubbles**: The bubbles that are forming are likely due to the air that was trapped in the dry soil. When the water is added, it displaces the air, causing it to escape in the form of bubbles.

4. **Composition of Air**: Air is a mixture of gases, primarily composed of nitrogen (78%) and oxygen (21%). Since the bubbles are coming from the soil, they contain air.

5. **Conclusion**: The bubbles observed by Usha contain air, which is a mixture of gases including oxygen and nitrogen. Therefore, the correct answer is that the bubbles contain air.

**Final Answer**: The bubbles contain air.

---