This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Which of the following are intracellular - 
Select and explain. 
A. Virus, B. Chlamydia, C. Rickettsia, D. All
D: All
Answer: D: All 
Explanation: Ans. is 'a' i.e., Virus; 'b' i.e., Chlamydia; 'c'i.e., Rickettsia