Which of the following is true about water temperature in freshwater ecosystems? a. Water temperature in all freshwater ecosystems is fairly consistent from top to bottom.
b. The top layer of a lake is warmer than the lower layer year-round.
c. Ponds have two distinct temperature layers.
d. None of the above

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.

the answer is false?

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.