If Some Cells in an Adult Mammal Are Lost, They

Short Answer

If some cells in an adult mammal are lost, they are lost forever and cannot be replaced. Which of the following cell types have such a limitation? Your answer would be a string composed of a subset of the letters A to E in alphabetical order, e.g. AE.
(A) Photoreceptive epithelium of the retina
(B) ? Cells of pancreatic islets
(C) Hepatocytes of the liver
(D) Auditory epithelium of the inner ear
(E) Olfactory epithelium of the nose