The most stable oxidation state of iron is:

Given below are two statements:
Statement $I$: Ferromagnetism is considered as an extreme form of paramagnetism.
Statement $II$: The number of unpaired electrons in a $Cr^{2+}$ ion $(Z=24)$ is the same as that of a $Nd^{3+}$ ion $(Z=60)$.
In the light of the above statements,choose the correct answer from the options given below:

Assertion : $Cr(VI)$ in the form of dichromate in acidic medium is a strong oxidising agent whereas $MoO_3$ and $WO_3$ are not.
Reason : $Mo(VI)$ and $W(VI)$ are found to be more stable than $Cr(VI)$.

The higher number of unpaired electrons are in

Why do the transition elements exhibit variable oxidation states?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: The first ionization enthalpy of $3d$ series elements is more than that of group $2$ metals.
Reason $(R)$: In $3d$ series of elements,successive filling of $d$-orbitals takes place.
In the light of the above statements,choose the correct answer from the options given below: