This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Structure without any membrane is 
Select and explain. 
A. Mitochondria, B. Nucleus, C. Nucleolus, D. Endoplasmic reticulum
C: Nucleolus
Answer: C: Nucleolus 
Explanation: Nucleolus is present in nucleus. Theirfunction is to produce ribosome. They are not enclosed by a membrane and contain proteins, DNA, RNA. (REF TEXTBOOK OF MEDICAL PHYSIOLOGY GEETHA N 2 EDITION, PAGE NO - 11)