1. Saturated air means air having maximum humidity or moisture. If we keep on adding moisture to saturated air the extra moisture will condense. And saturated air will become unsaturated air at that temperature.

2. Since amount of liquid is continuously decreasing that means evaporation is taking place.

3. Now during vaporization, moisture is being continuously added to air above liquid. Temperature is changing continuously.

4. So, vapors in remaining part is unsaturated as air contains extra moisture.