I'm pretty sure it's answer D. It's the only answer choice that really makes sense.
Answer:
Chronic Kidney Disease - Learn about the causes, symptoms, diagnosis ... Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys' ability ... the kidneys cannot absorb water from the urine to reduce the volume of urine ... in the blood can damage nerve cells in the brain, trunk, arms, and legs
Well, an endoskeleton is an internal skeleton, like humans have.
Pro: Bones do not get broke as easily, since they are inside of the body. Bones that break also heal more quickly in an endoskeleton, since they have tissue and blood surrounding it and transferring nutrients.
Con: The flesh can get easily damaged. There is no shedding with endoskeletons, so a new skeleton cannot be grown in the event of an injury.