Pressure decreases with increasing altitude. The pressure at any level in the atmosphere may be interpreted as the total weight of the air above a unit area at any elevation. At higher elevations, there are fewer air molecules above a given surface than a similar surface at lower levels.
C. increased stirring i think
Well let’s put it this way. To find the neutrons you subtract the atomic atomic Nuremberg from the atomic mass. So
Mass=81-Number=28
81-28=53
Final answer is 53.