**Reactivity Series: Introduction**

The reactivity series is a list of metals arranged in order of their reactivity, from the most reactive to the least reactive. This series helps us understand the relative reactivity of metals and their ability to displace another metal from its compound.

**Copper and its Reactivity**

Copper is a moderately reactive metal. It does not react with water or steam, but it reacts slowly with oxygen in the air to form copper oxide. However, copper does not displace hydrogen from acids and is therefore less reactive than metals such as aluminium, iron, and zinc.

**Comparing the Reactivity of Metals**

To determine which metal comes below copper in the reactivity series, we need to compare the reactivity of copper with the given options: aluminium, iron, silver, and zinc.

- Aluminium: Aluminium is more reactive than copper. It reacts with oxygen in the air to form a thin layer of aluminium oxide, which protects it from further oxidation. It also displaces copper from copper sulfate solution, indicating its higher reactivity than copper.
- Iron: Iron is more reactive than copper. It reacts with oxygen in the air to form iron oxide, commonly known as rust. It also displaces copper from copper sulfate solution, indicating its higher reactivity than copper.
- Silver: Silver is less reactive than copper. It does not react with oxygen in the air, water, or acids. Therefore, it is placed below copper in the reactivity series.
- Zinc: Zinc is more reactive than copper. It reacts with oxygen in the air to form zinc oxide. It also displaces copper from copper sulfate solution, indicating its higher reactivity than copper.

**Conclusion**

Among the given options, silver comes below copper in the reactivity series. Silver is less reactive than copper and does not readily react with oxygen, water, or acids. Therefore, the correct answer is option 'C' - Silver.