QUESTION:
Which line shows how the oxygen concentration of the water changes after excess fertiliser has entered a stream?
OPTIONS:
A: more oxygen downstream
B: more oxygen near fertiliser run-off and downstream but less oxygen in the middle
C: same oxygen everywhere
D: less oxygen near fertiliser run-off and downstream but more oxygen in the middle
NOTE:
The correct answer is B but I need an explanation as to why. I thought the answer was A and got it wrong.
![QUESTION Which line shows how the oxygen concentration of the water changes after excess fertiliser has entered a stream OPTIONS A more oxygen downstream B more class=](https://us-static.z-dn.net/files/d82/0f38354815140235c86c4cdd6150ee37.png)