Which is a reason for the rise of nitrate levels in ground water?
a) overuse of fertilizers
b) ammonification by animals
c) soil erosion at grasslands
d) nitrogen fixation by azotobacter

i believe the correct answer from the choices listed above is the first option. the scientists need to look at the   validity of data, claims, hypotheses, and observations before  developing an argument. they base their arguments on facts that are present and they make sure they have proofs. 

explanation:

cells spend most of their time in interphase