Match the following:

List-$I$	List-$II$
$A$. Titanium	$I$. Non-metal
$B$. Fluorine	$II$. Transition metal
$C$. Tellurium	$III$. Lanthanoid
$D$. Dysprosium	$IV$. Metalloid

Which of the following pairs of elements does $NOT$ represent chemical twins?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Generally, $3d$ transition metals have high melting points.
Reason $R$: Involvement of $3d$-electrons in addition to $4s$-electrons in the interatomic metallic bonding.
In light of the above statements, choose the most appropriate answer from the options given below:

$A$ transition metal $X$ has a configuration $[Ar]3d^4$ in its $+3$ oxidation state. Its atomic number is

Which of the following has the maximum number of unpaired electrons?

The hardness of $Cr$ is due to $......$ and metallic lustre is due to $.......$