Answer :

(a)

i) ‘A; Circular DNA/Plasmid ‘B’ Bacteriophage

ii) (Plasmid)-Can carry foreign gene into the host cell/acts as cloning vector/has selectable marker/ independent of the control of chromosomal DNA/ high copy number (Bacteriophage) -Cloning vector have the ability to replicate in bacterial cells / independent of the control of chromosomal DNA / high copy number per cell.

or

(b) Treating bacteria with specific concentration of calcium (ions)which increases the efficiency with which DNA enters the bacteria through pores in its cell wall , recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42°C (heat shock), then putting them back on ice.