What can you conclude about two thermometers, one which is at 25 ˚C and the other which is at 20 ˚C?

Either the surrounding environment is slightly different over little distance, or one of the thermometers are defective,.

Explanation:

"d.) carbon dioxide and hydrogen sulfide"

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.