Which term refers to the internal vertebrate structure composed of bone and cartilage that protects the soft organs, including the bones left after decomposition?

• A. Cartilage
• B. Remains
• C. Optical
• D. Skeleton

Answer: (D)

The main idea here is the body's internal framework that protects vital organs, built from bone and cartilage. This framework is the skeleton, which comprises the bones (and their cartilaginous parts) and serves to shield the brain, heart, lungs, and spinal cord. It’s also the durable structure that can remain after soft tissues have decomposed, so bones left after decomposition are part of the skeleton. Cartilage alone is just a tissue, not the entire protective framework. Remains is a general term for what’s left after death, not the specific anatomical concept, and optical has no relevance here. So the correct term that fits is skeleton.