The correct answer is Silver fish Explanation & Key Takeaways: • The organism among the given options that does NOT have a skeleton is a Silverfish. • Silverfish are insects, more specifically in the order of Thysanura. • Unlike vertebrates (animals with a backbone, like salmon, shark, and ratfish), they don't have internal skeletal structures. • Instead, they possess a hard outer shell or exoskeleton made of a substance called chitin. • The exoskeleton works differently to an internal skeleton (endoskeleton). • It provides some structure and protection, like an endoskeleton, but it doesn't assist with internal organ support to the same extent. • Silverfish will molt, shedding their exoskeleton as they grow, which is different from the continuous growth seen in endoskeletons. • Salmon, Shark, and Ratfish are fish, belonging to classes Actinopterygii, Chondrichthyes, and Chimaeriformes, respectively. • They all possess internal skeletal structures. • In the case of salmon, there is a bony skeleton. • Sharks and ratfish have skeletons made up of cartilage rather than bone, disregarding the difference in material, it is indeed an internal skeleton.