B. Assertion and reason both are true, but the reason is not the correct explanation of assertion.

C. The assertion is true, the reason is false.

D. The assertion is false the reason is true.

Assertion and reason both are true, but the reason is not the correct explanation of assertion.

In [Cr(H₂O)₆]Cl₂ the oxidation state of central metal atom Cr is x=-(-2)=+2 and for [Fe(H₂O)₆]Cl₂ also the oxidation state of Fe is +2. Hence, both of them are in their lower oxidation states and that means they can further be oxidised and therefore they are reducing in nature. Also, they have enough d-electrons to donate to other ligands and have more compounds formed.

And the corresponding structures are:

and