This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Techniques in molecular biology, Subject name: Biochemistry
Which of the following can be used as vector for Gene therapy 
Select and explain. 
A. Viruses, B. Liposomes, C. Plasmids, D. All of these
D: All of these
Answer: D: All of these 
Explanation: Vectors used for gene delivery : Viral Vectors Non-viral Vectors Retroviruses Liposomes Adenoviruses Plasmids Herpes simplex viruses Physical methods