An estimated % of adults 51 years and older lose the ability to absorb vitamin b12 due to atrophic gastritis.

20%-30% in adults at the age of 51 years old and 10% to 15% in the age of 60 and older.

The direction a chemical reaction occurs is represented by an arrow 

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.