It is a column of elements in the periodic table of the chemical elements.
The correct answer is B. Platinum is the transition element among the choices. The elements belonging to this group are those having a partially filled d or f subshell. It usually refers to the d-block transition elements of the periodic table.
Start by writing the atoms balance:

Now, determine the change of oxidation states:

has oxidation state 0, so each N has to gain 3 electrons to become

.
That, means that you need 6 electrons to balance the charges, resulting in:
And the answer is 6 mole of electrons.
The sun i believe is one and wind