A study was conducted to determine the effect of weather on varieties of corn grown for grazing by cattle in Alberta, Canada. To conduct the study, five varieties of corn were considered (one grazing, one short-stature, and three conventional) with harvesting of crops conducted on four occasions (two dates in September, one in December, and one in January). The experimental treatments were assigned at random to plots of land at each of two different locations in Alberta in order to control for natural variations in location. The crude protein concentration of the harvested corn was determined. The two Alberta locations used in the study were Lacombe and Brooks. In this study location is considered to be what kind of variable? A) A factor variable
B) A treatment variable
C) A blocking variable
D) A lurking variable
E) A control variable