Given below are two statements: One is labelled as "Assertion A" and the other is labelled as "Reason R".
Assertion A: In the complex Ni(CO), and Fe(CO)s, the metals have zero oxidation state.
Reason R: Low oxidation states are found when a complex has ligands capable of π-donor character in addition to the o-bonding.
In the light of the above statements, choose the most appropriate answer from the option given below.