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
Natural method of horizontal gene transfer among bacteria includes -a) Electroporationb) Transductionc) Transformationd) Conjugatione) Mutation 
Select and explain. 
A. abc, B. acd, C. bcd, D. bd
C: bcd
Answer: C: bcd 
Explanation: None