The acceptable level of thermal comfort for humans is defined as the range of temperature at which most people feel comfortable without the need for extra heating or cooling.
According to standard environmental health guidelines, the comfort zone for indoor air temperature is typically 20$^\circ$C to 25$^\circ$C.
Temperatures below 20$^\circ$C may feel too cold, and above 25$^\circ$C may start to feel warm and less comfortable for sedentary work.
Therefore, the correct acceptable range is 20$^\circ$C - 25$^\circ$C.