Which is responsible for controlling the copy number of the linked DNA in a plasmid?

The correct option is A Ori
Plasmid
Plasmids are extranuclear, circular, double stranded DNA. They are usually used as vectors in genetic engineering.

Copy number
Number of copies of a given plasmid present in the host cell is called the copy number.

Cloning sites
Recognition sites or cloning sites are specific nucleotide sequences, present on the plasmid DNA, that can be recognised and cleaved by restriction endonucleases for incorporation of the gene of interest.

Origin of replication
Origin of replication is a nucleotide sequence that initiates replication in a plasmid without being dependent on genomic DNA for replication. Linking of the gene of interest to the ori will ensure the formation of multiple copies of the gene.

Restriction endonucleases
Restriction endonucleases are the enzymes which cleave the DNA by digesting phosphodiester bonds at the specific sequences within the DNA.
Examples include EcoR I.
They help in cutting the vector and the DNA of interest to create the rDNA.

Insertional inactivation
Insertional inactivation is the process of inactivation of a marker gene by the insertion of foreign gene in its coding sequence.
For example, insertion of a foreign gene in the coding sequence of 𝛽-galactosidase gene, synthesize a non-functional enzyme, which does not convert chromogenic substrate into a product. Hence only the non-recombinant colonies produce blue colour due to the presence of chromogenic substrate and absence of insert. In this way, it helps in the selection of recombinants.

Final answer
(B) Ori