This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basics of DNA, Subject name: Biochemistry
Which of the following is an example for facultative heterochromatin? 
Select and explain. 
A. Centromere, B. Telomere, C. Barr body, D. All of the above
C: Barr body
Answer: C: Barr body 
Explanation: Heterochromatin is of two types: Constitutive heterochromatin Facultative heterochromatin Centromeric DNA Telomeric DNA Barr body (condensed X-chromosome) Condensed, inactive Decondenses during gametogenesis