Answer:
Mammals are different from fish, reptiles or birds
Explanation:
This is the correct answer because since dolphins are mammals, they are very different from the other types of animals such as fish, reptiles, or birds; this is emphasized in this paragraph ;)
The repetition of the r sound in "heaR", "Rushing", "RoaRing", and "shRill" suggests the image and sound of the train rushing past. When something fast moves by you, there's a rush of air that flies by, and this sound and movement of air, mixed with the grinding of the train on the tracks is meant to be represented by the 'r' sound, based on the consonance in the line.