DNA and RNA are both important nucleic acids. They have similarities and differences structurally.
Use the Venn diagram to compare the two nucleic acids

1. a tropical dry forest carries out more rapid nutrient cycling

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

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.