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: Biochemistry
DNA supercoiling is done by : 
Select and explain. 
A. DNA polymerase I, B. DNA polymerase II, C. DNA topoisomerase, D. DNA gyrase
D: DNA gyrase
Answer: D: DNA gyrase 
Explanation: D i.e. DNA gyrase