The flow chart shows the process of eutrophication. What should appear at step X and step Y in the flow chart?
- Astep X: decrease in nitrate ion concentration; step Y: decreased dissolved oxygen concentration
- Bstep X: increase in nitrate ion concentration; step Y: decreased dissolved oxygen concentration
- Cstep X: decrease in nitrate ion concentration; step Y: increased dissolved oxygen concentration
- Dstep X: increase in nitrate ion concentration; step Y: increased dissolved oxygen concentration