A(n) can scan a culture of bacteria or a sample of blood and differentiate between blood cells.

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.

"d.) carbon dioxide and hydrogen sulfide"

not too sure but maybe in the hot springs.