Question

Where in a river would you find fish that are adapted to low light and low oxygen levels?
a) at the source
b) in the mid-river
c) near the mouth
d) no place in the river is characterized like this.

Answer 1

C) near the mouth

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The mouth is where the river flows into another body of water and there is least oxygen here. The river slows down here and that decreases dissolve oxygen.