Which animal group usually has an outer shell that is not jointed?Group of answer choicesmolluscsechinodermsannelidscnidariansarthropods

To determine which animal group usually has an outer shell that is not jointed, let's analyze the options given:

1. Molluscs: This group includes animals such as snails, clams, and octopuses. Many molluscs have a hard outer shell that is typically unjointed.

2. Echinoderms: This group includes starfish and sea urchins. They do not have a traditional shell; instead, they have a hard endoskeleton made of calcareous plates.

3. Annelids: These are segmented worms, such as earthworms and leeches. They do not have a shell.

4. Cnidarians: This group includes jellyfish, corals, and anemones. They lack an outer shell structure.

5. Arthropods: This group includes insects and crustaceans. They have an exoskeleton, but it is segmented and jointed.

Conclusion

Based on the descriptions, the correct group that usually has an outer shell that is not jointed is molluscs.