Final answer:
Arthropods have an open circulatory system, which means that hemolymph flows freely through the body cavity and direct contact with organs, not a closed circulatory system. They also possess a rigid exoskeleton made of chitin and a variety of appendages adapted for different functions. Option b.
Step-by-step explanation:
Arthropods are a diverse group of organisms known for their segmented bodies and jointed appendages.
One characteristic that sets them apart from many other animal groups is their open circulatory system. In this system, hemolymph - a fluid analogous to blood - is pumped into the body cavity where it makes direct contact with the organs, rather than being confined to vessels as seen in a closed circulatory system.
Other key features include their rigid exoskeleton made of chitin, which provides support and protection but requires molting to accommodate growth.
Additionally, these creatures possess a range of appendages, including legs, antennas, and mouthparts, which are adapted for various functions like locomotion, sensing, and feeding. Arthropods have diverse respiratory systems, such as gills, tracheae, and book lungs, to facilitate gas exchange in different environments.
Given these attributes, the characteristic that does not apply to arthropods is a closed circulatory system. Instead, their open circulatory architecture allows hemolymph to flow freely through their body cavities. Option b.