Question

Animals of which group are not fresh water?
A. Crustacea
B. Insecta
C. Echinodermata
D. Sponge

Answer 1

Hint: Animals live in a variety of habitats. Among the marine animals, a few living near the water surface are pelagic and those living in depths of ocean are abyssal. A few others living near the oceanic bottom are littoral and still other leading sedentary life on the bottom are benthic.

Complete answer:
Crustacea
Crustacea are aquatic animals that belong to phylum Arthropoda. They have habitat in both fresh water as well as marine ecosystems. Their body is generally divisible into two parts- cephalothorax and abdomen. They have typical biramous appendages and they respire either by gills or through body surface. The excretion occurs through coxal glands or Green glands. The examples of Crustacea are Water flea (Daphnia), prawn (Palaemon), crab, hermit crab, crayfish (Astacus), and Sacculina.
Insecta
The animals of this class are found in all habitats- air, water and land. They have habitat in both freshwater and marine water. Their body is clearly divisible into three parts- head, thorax and abdomen. Thorax has three pairs of jointed legs and one or two pairs of wings. They have a head with a pair of compound eyes, one pair of antennae and three pairs of jaws. They respire through trachea. For example, Silverfish (Lepisma), dragon fly, house fly (Musca), mosquito, ant, honey bee (Apis).
Echinodermata
Echinodermata are exclusively marine animals. They are pentamerous, radially symmetrical animals with spiny skin. They have an unsegmented, star-shaped, globular, spherical, flat or branched body. They have an indistinct head. Their locomotion is by tubular feet. For example, Star fishes.
Sponge
Porifera are pore bearing animals and commonly called sponges. They have cellular organization, cell aggregate plan and are mostly asymmetrical. They are mostly marine but about 150 sponge species inhabit fresh water, e.g. Spongilla.
So the correct answer is C. Echinodermata.

Note: Sponges are simplest diploblastic animals. Crustacea and Insecta are the groups of phylum Arthropoda. Arthropoda is the largest phylum of Animal kingdom includes jointed legged animals that are cosmopolitan in distribution.