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: Medicine
Mutation that completely disrupt the function of the gene used in which of the following technique: 
Select and explain. 
A. Knock-out, B. Non-sense mutation, C. Restrictin fragment length polymorphism, D. None
A: Knock-out
Answer: A: Knock-out 
Explanation: A i.e. Knock-out