Select reducing agent out of given options:

Because ${\mathrm{Eu}}^{3+}$ is more stable than ${\mathrm{Eu}}^{2+}, {\mathrm{Eu}}^{2+}$ is an effective reducing agent. Detailed response: Eu2+ electronic configuration is $4{\mathrm{f}}^7 6{\mathrm{s}}^2$ Electrons evolve during oxidation. As a result, after two electrons are removed, it achieves a stable half-filled electronic configuration that acts as a strong reducing agent.

Hence,${\mathrm{Eu}}^{2+}$is reducing agent.