A student has strips of zinc, copper and silver, and solutions of their nitrates…

Step 1. (a). Copper is a stronger reducing agent than silver, so it reacts: $\text{Cu} + 2\text{Ag}^+ \rightarrow \text{Cu}^{2+} + 2\text{Ag}$.

Step 2. (b). Silver is the weaker one, so there is no reaction.

Step 3. (c). Zinc beats copper: $\text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}$.

Step 4. (d). Copper is weaker than zinc, so there is no reaction.

Step 5. The order. The two reactions that work show zinc beats copper and copper beats silver.