The point where all the three state (solid, liquid, vapour) of `H_2O` exist is known as

Options

A. Single point
B. Double point
C. Triple point
D. Solid point

Answer

To solve the question regarding the point where all three states (solid, liquid, and vapor) of H2O exist, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the States of Matter**:
- Water (H2O) can exist in three states: solid (ice), liquid (water), and vapor (steam).

2. **Defining the Concept**:
- The point where all three states coexist is a specific condition of temperature and pressure.

3. **Identifying the Point**:
- This specific point is known as the "triple point." At the triple point, the three phases of a substance can coexist in thermodynamic equilibrium.

4. **Temperature and Pressure of the Triple Point**:
- For water, the triple point occurs at a temperature of approximately 273.16 K (0.01 °C) and a pressure of about 611.657 pascals.

5. **Conclusion**:
- Therefore, the answer to the question is that the point where all three states of H2O exist is called the "triple point."

### Final Answer:
The point where all the three states (solid, liquid, vapor) of H2O exist is known as the **triple point**.

---