Which group of animals does the term 'invertebrate' encompass?

The term 'invertebrate' refers to a diverse group of animals that do not possess a backbone or spinal column. This includes many different species, such as insects, crabs, jellyfish, worms, and many others, highlighting the vast diversity of life forms within the invertebrate category.

Option C accurately describes this group by specifying examples like insects and crabs, which are common representatives of invertebrates. By encompassing various habitats, including terrestrial and aquatic environments, the term reflects the broad classification of all animals lacking a vertebral column rather than being restricted to a specific type or location of animals.

In contrast, the other choices either limit the definition to vertebrates, a specific subgroup of animals with backbones, or to a narrower scope that does not adequately represent the full range of invertebrate diversity. Therefore, the correct answer captures the essence of what invertebrates are and includes representative examples that belong in this category.