Write the `S.I`. unit of temperature.

Answer

To answer the question regarding the S.I. unit of temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding SI Units**:
- The International System of Units (SI) is a standardized system used globally for scientific measurements.

2. **Identifying the Unit for Temperature**:
- In the SI system, each physical quantity has a specific unit. For temperature, the SI unit is defined.

3. **Defining the SI Unit of Temperature**:
- The SI unit of temperature is **Kelvin**.

4. **Symbol for Kelvin**:
- The symbol used to represent Kelvin is **K**.

5. **Relation to Other Temperature Scales**:
- It is important to note that the Kelvin scale is related to the Celsius scale. The difference between the freezing point (0°C) and boiling point (100°C) of water is the same as that in Kelvin (273.15 K and 373.15 K respectively), meaning that a change of 1 degree Celsius is equivalent to a change of 1 Kelvin.

### Final Answer:
The S.I. unit of temperature is **Kelvin (K)**.

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