Answer: Option A. "DNA (genes)"
Step-by-step explanation:
Cloning is defined a process to create clones or copies of DNA fragments either naturally or artificially.
DNA is a basic required factor for cloning in both natural and artificial cloning. In the process of cloning amplification of DNA fragments takes place and majorly used to make multiple copies of amplified DNA.
The process of cloning starts with the breaking of DNA strand (fragmentation) followed with the attachment of pieces of DNA together in required sequence (litigation), after litigation new pieces of DNA are allowed to insert into the cells (transfection) and at the end successfully transfected cells are selected (screening).
Hence, DNA are required factor for cloning.