Standard electrode potential of three metals X, Y and Z are -1.2 V, +0.5 V and -3.0 V, respectively. The reducing power of these metals will be:
Y>Z>X
X>Y>Z
Z>X>Y
X>Y>Z
We know that,
The higher the reduction potential, the higher will be oxidation agent or the lesser will be the reducing agent.
The lesser the reducing agent, the lesser will be reducing power
So,
Hence,
So, option 3 is correct.