What is the large extrachromosomal plasmid found in Agrobacterium tumefaciens that has the ability to induce tumors called?

Polyethylene glycol method is used for

$I.$ Bacteriophages are $...A...$ infecting $...B....$
$II. ...C...$ are hybrid vectors derived from plasmids which contain $cos$ site of $\lambda$ phage.
$A, B$ and $C$ in above statements refer to:

Which of the following acts as a vector?

Explain the following terms in the context of Biotechnology:
$(a)$ $PCR$
$(b)$ Restriction enzymes and $DNA$
$(c)$ Chitinase

Which of the following hydrolases cleaves internal phosphodiester bonds in a polynucleotide chain?