$DNA$ polymerase links nucleotides by forming which type of bond?

$A$ $DNA$ molecule in which both strands have radioactive thymidine is allowed to duplicate in an environment containing non-radioactive thymidine. What will be the correct number of $DNA$ molecules that contain some radioactive thymidine after three duplications?

Match the columns.

Column - $I$	Column - $II$
$(a)$ Helicase	$(1)$ Joining of nucleotides
$(b)$ Gyrase	$(2)$ Opening of $DNA$
$(c)$ Primase	$(3)$ Unwinding of $DNA$
$(d)$ $DNA$ Polymerase $III$	$(4)$ $RNA$ Priming

$DNA$ repairing is done by

Match the following columns:

Column-$I$ (Enzyme)	Column-$II$ (Function)
$P$. $DNA$ Polymerase	$I$. Synthesizes $DNA$ strand
$Q$. $DNA$ Helicase	$II$. Breaks $H$-bonds of $DNA$ strands
$R$. $DNA$ Ligase	$III$. Joins $DNA$ fragments

Identify the given model.