This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasitology, Subject name: Microbiology
[{'content': 'Which of the following show regressive metamorphosis? \nSelect and explain. \nA. Hydatid cyst, B. Cysticercoid, C. Cysticercus bovis, D. Cysticercus cellulosae', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Hydatid cyst(Ref: D.R. Arora, 3rd/e, p. 141)* Regressive metamorphosis: Sometimes, hydatid cyst (containing protoscolices) may rupture in intermediate host to release its content in the tissue. If such a patient survives, the released protoscolices may revert to hydatid cyst instead of developing into an adult worm (Normally protoscolex give rise to adult worm).", 'role': 'assistant'}]