5. Membrane receptors are specialized proteins that take part in communication between the cell and the outside world. The membrane protein receptor can be subdivided into three parts or domains. The portion of the protein in the E zone is extracellular (outside of the cell). The P zone is the plasma membrane and the l zone is intracellular (inside of the cell).

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.