Salt concentration is the factor among the following factors given in the question that does not vary between a fast flowing river and a pond that receives no water input. The correct option among all the options that are given in the question is the second option. I hope the answer comes to your help.
The physical distance that separates them on the chromosome.
NREM 3
The correct answer is: Stage 3
I hope that helped! c:
Mid-ocen ridges is correct