$3d-$ metal ions exhibit paramagnetic behavior because . . . . .

Which of the following elements has the highest number of unpaired electrons in its ground state?

In the series $Sc (Z=21)$ to $Zn (Z=30)$,the enthalpy of atomisation of zinc is the lowest,i.e.,$126 \ kJ \ mol^{-1}$. Why?

Assertion : Borax bead test is not suitable for $Al(III)$.
Reason : $Al_2O_3$ is insoluble in water.

The valence shell electronic configuration of $Cr$ and $Cu$ atoms, respectively, are

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: In $T \ell I_{3}$,isomorphous to $CsI_{3}$,the metal is present in $+1$ oxidation state.
Reason $R$: $T \ell$ metal has fourteen $f$ electrons in the electronic configuration.
In the light of the above statements,choose the most appropriate answer from the options given below: