Generally,the Height Above the Ground for a Weather Thermometer Placement

Generally,the height above the ground for a weather thermometer placement is approx.4 ft.,because:

A) it is easier for short people to read.
B) temperature extremes occur if placed too close to the ground.
C) because that is the way it has always been done.
D) of overall ease of use.
E) if all thermometer's are placed at that height,then accurate comparisons between recording stations can occur.