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
Obligatory intracellular organism is ? 
Select and explain. 
A. Mycoplasma, B. Chlamydae, C. Cryptococcus, D. H.pylori
B: Chlamydae
Answer: B: Chlamydae 
Explanation: Ans. is 'b' i.e., Chlamydia