Approximately 9l of fluid enters the gastrointestinal tract daily, 2l by ingestion and 7l by secretion. almost percent of this volume is reabsorbed so that fecal fluid loss is only 100-200 ml/d.

Ibelieve the answer is relative humidity  because it makes more sense that way. solar flares usually occur in space it doesn't affect the earth, well it could but it wont make a significant damage.  latitude is land it doesnt do anything. prevailing winds, i dont know the correct meaning for this but i doubt that affects the land so it has to be relative humidity.