Identify the metals on the basis of their reaction with water.

A - reacts violently with cold water

B - reacts with steam only

C - does not react with water

The correct option is Potassium, Iron, Copper.

To identify the correct set of metals, let us analyze the reactivity of each metal with water based on the metal reactivity series:

1. Metal A (Reacts violently with cold water):
Metals high in the reactivity series, such as potassium (K) and sodium (Na), react violently with cold water to produce metal hydroxide and hydrogen gas, releasing a large amount of heat. Thus, Metal A is Potassium.

2. Metal B (Reacts with steam only):
Metals of moderate reactivity, such as iron (Fe), zinc (Zn), and aluminium (Al), do not react with cold or hot water. However, they react slowly with steam to form their respective metal oxides and hydrogen gas. Thus, Metal B is Iron.

3. Metal C (Does not react with water):
Metals placed below hydrogen in the reactivity series, such as copper (Cu), gold (Au), and silver (Ag), are very unreactive and do not react with water at all (neither cold water, hot water, nor steam). Thus, Metal C is Copper.

Comparing these observations with the given options, the correct matching sequence (A, B, C) is Potassium, Iron, Copper.