Which statement correctly describes how the amount of oxygen in earth’s atmosphere has changed over time?

it has one origin of replication, but it proceeds in two directions - d)

answer: i don't know

explanation:

you need to provide a picture, otherwise i can't tell you.

if you can provide one, i'd be more than happy to you with this!

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.

the correct answer is 2 and 4