Final answer:
The group made up solely of carnivores is arachnids, as most arachnids, such as spiders, are carnivorous. The other groups listed contain a variety of feeding habits including herbivory and omnivory. The correct option is A.
Step-by-step explanation:
The question asks which of the following groups is made up solely of carnivores: arachnids, insects, vertebrates, mammals, or flatworms. Carnivores are animals that primarily eat other animals.
A review of the groups mentioned reveals that not all members within the group's insects, vertebrates, mammals, and flatworms are carnivores, as these groups contain herbivores and omnivores as well. However, the majority of arachnids, which include spiders, are carnivorous, feeding on insects and sometimes even small vertebrates.
Therefore, the correct answer is arachnids, as they are predominantly carnivorous, and none of the other listed groups consist entirely of carnivores. For instance, among mammals, there are insectivores like shrews, omnivores like humans, and even herbivores. Insects like ladybugs are carnivorous, but this group also contains herbivorous and omnivorous species.