Answer:
Canyon Creek<Wooded Marsh<Rivers Edge
Explanation:
When hike length was 3 km and there are 8 animals, the number of animals seen per kilometer will be (8/3) = 2.67 animals/km
When hike length was 8 km and there are 20 animals, the number of animals seen per kilometer will be (20/8) = 2.5 animals/km
When hike length was 15 km and there are 35 animals, the number of animals seen per kilometer will be (35/15) = 2.34 animals/km
Canyon Creek<Wooded Marsh<Rivers Edge is the required order.