Which of the following statements regarding the magnetic properties and electronic configurations of transition metal ions is correct?

1. A.The ion ${\text{Mn}}^{2+}$ has a $d^5$ configuration and is diamagnetic.
2. B.The ion ${\text{Cu}}^{+}$ has a $d^{10}$ configuration and is diamagnetic.
3. C.The ion ${\text{Fe}}^{3+}$ has a $d^5$ configuration and is diamagnetic.
4. D.The ion ${\text{Zn}}^{2+}$ has a $d^9$ configuration and is paramagnetic.