Lorna wants to know if the size of the cookie influences how long it takes to bake. She places different amounts of cookie dough on baking sheets and times how long it takes for the cookies to bake. What is the independent variable in her investigation?

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.