Why is it important for us to have our
lungs inside our bodies?

A. to keep them moist

B. to make them more eficient

C. to increase surface area to keep them moist be

Most likely to keep them moist, but I would argue that protecting them from outside elements is equally important if not more so. If the lungs were on the outside, then the water would evaporate away so thats likely what your teacher is going after.

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.