List three methods used to prevent the evaporator from becoming too cold and freezing

The first one is have the refrigerant level checked by a qualified professional. The technician will be checking any possible leak, damage and conduct test on the system. Second is to ensure airflow. Change the filter regularly, usually about every three months or maybe monthly, depending on its usage. Have the coils cleaned by a professional if it is already dirty. The third method is to not use your air conditioner when the outside temperature is below 60º. You will be saving energy and money on utility costs by just opening the windows on cool days.

Following are some preventive measures for the freezing of the evaporator:

1. Check the air flowing through the supply registers.  Air should not be warmed or trapped inside.

2. There should not be a moisture built up inside.

3. Condensate lines are the part of your HVAC system that drains away excess moisture from humidity. This moisture, condensed into water, travels through pipes to a floor drain. If the water is stuck in one place because of a clogged pipe, it can freeze. so, the water should not be stuck in one place.

4. Shut the unit off if evaporator has got frozen and try to melt the ice.

it's c. (to reduce the greenhouse effect/carbon gasses)