There are 20 mice in a 5 m2 field ecosystem. the population density of mice is

4 per m2
5 per m2
20 per m2
25 per m2

answer: 2

explanation:

yes

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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.

the three components of a nucleotide are the nitrogenous base, the phosphate group and the five-carbon sugar.