Which option distinguishes the barn structure that would best compensate for lack of electricity?

a barn with no windows and a dirt floor
a barn with the windows facing the east
a barn with the windows facing the south
a barn with no windows and a concrete floorplan

"six months ago, several of molly's friends joined the trimtime fitness center. each of them participated in trimtime's weight-reduction and fitness regimen. all reported substantial weight reduction, and all are visibly slimmer. molly is convinced. she joins trimtime and enrolls in the program, hoping and expecting to see the same results. she is especially delighted to learn that trimtime had adjusted its program to make it even more effective in a shorter period of time." what is the feature in question/attribute of interest in this argument?