A. Shrimp, with a segmented body and hard armor, is an arthropod;

B. Eel lives in the water all its life, breathing with gills and swimming with fins, which is consistent with fish Characteristics of fish;

C. Soft-shelled turtles lay eggs and breathe with lungs, so they are reptiles;

D. Jellyfish have a simple structure, with a digestive cavity in the body, a mouth but no anus. , belonging to coelenterates.

So choose: B