Step 1: Count d electrons first:
After losing 4s electrons: $\text{Cr}^{2+}$ is $d^4$, $\text{Mn}^{2+}$ is $d^5$, $\text{Fe}^{2+}$ is $d^6$, $\text{Co}^{2+}$ is $d^7$, $\text{Ni}^{2+}$ is $d^8$.
Step 2: Convert to unpaired electrons:
For up to five d electrons, all are unpaired: $d^4 \to 4$, $d^5 \to 5$. After the half-filled point, extra electrons pair up: $d^6 \to 4$, $d^7 \to 3$, $d^8 \to 2$.
Step 3: Match pairs:
(A) $4, 5$. (B) $3, 2$. (C) $4, 4$. (D) $3, 4$. Only (C) matches.
Final Answer:
Option (C), both have 4 unpaired electrons.
\[ \boxed{\text{Fe}^{2+} \text{ and } \text{Cr}^{2+} \text{ (C)}} \]