Answer: Option B
:
B
Option a) – Number of oxidation states increases as we move from group 3 to group 7 in same period.
Option b) – V${}^{2+}$(3 unpaired electrons) %undefined Cr${}^{2+}$ ( 4 unpaired electrons) = Fe${}^{2+}$ (4 unpaired electrons) %undefined Mn${}^{2+}$ ( 5 unpaired electrons)
Option c)- Ionic size decreases from left to right in the same period.
Option d)- As the standard reduction potential value for the couple M${}^{3+}$/M${}^{2+}$ decreases, the stability of M${}^{3+}$ ion in aqueous solution increases. Thus, correct increasing order of stability of M${}^{3+}$ ions in aqueous solution is: Co${}^{3+}$ < Fe${}^{3+}$<Cr${}^{3+}$ <Sc${}^{3+}$.