What is the term used to denote the critical temperature at which the air becomes saturated with vapour and below which the condensation is likely to begin ?

Options

A. Condensation point
B. Evaporation point
C. Dew point
D. Point of critical temperature

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for a specific term that describes the critical temperature at which air becomes saturated with vapor and below which condensation is likely to occur.

2. **Identifying the Term:**
The term that describes this phenomenon is known as the "dew point."

3. **Defining Dew Point:**
The dew point is defined as the temperature to which air must be cooled for it to become saturated with water vapor. At this temperature, the air can hold no more moisture, and any further cooling will lead to condensation of the vapor into liquid water.

4. **Conditions for Dew Point:**
At the dew point, both the air pressure and the water content remain constant. This means that the amount of moisture in the air does not change while the temperature decreases to the dew point.

5. **Understanding Condensation:**
If the air is cooled further below the dew point, the water vapor present in the air will begin to condense into liquid water. This process is what we refer to as condensation, where the vapor phase transitions to the liquid phase.

6. **Conclusion:**
Therefore, the term used to denote the critical temperature at which the air becomes saturated with vapor and below which condensation is likely to begin is the "dew point."

**Final Answer:**
The term is "dew point."

---