The metal ions that have the calculated spin-only magnetic moment value of 4.9 B.M. are :
A. ${\rm{C}}{{\rm{r}}^{2 + }}$
B. ${\rm{F}}{{\rm{e}}^{2 + }}$
C. ${\rm{F}}{{\rm{e}}^{3 + }}$
D. ${\rm{C}}{{\rm{o}}^{2 + }}$
E. ${\rm{M}}{{\rm{n}}^{3 + }}$
Choose the correct answer from the options given below: