Atomic structure and the Periodic Table — practice question

Cr, Co, Fe and Mn are all transition elements. Which particles contain the same number of electrons?

• A$\text{Co}^{2+}$ and $\text{Cr}$
• B$\text{Co}^{2+}$ and $\text{Fe}^{3+}$
• C$\text{Cr}$ and $\text{Mn}^{2+}$
• D$\text{Fe}^{3+}$ and $\text{Mn}^{2+}$