Shading by vegetation often proves more effective than shading by overhangs and fins: a. because vegetation is easily replaced if damaged b. because vegetation is renewable and other devices are not c. because vegetation looks more sustainable than overhangs and the like d. because vegetation growth better matches seasonal needs for shading

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

on island x the species needed to adapt because they were being subject to predators which didn't inhabit island y.  

i'd have to say the answer is probable the second option "the geosphere interacting with the atmosphere"