Evolution occurs at which level of biological organization? select one: a. species b. cells c. individuals d. populations

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

not sure if this is what you'r looking for nnew= nold