54. This non metal is used in the purification of water.

1. Bromine

2. Iodine

3. Chlorine

4. Sulphur

The correct option is C

Chlorine

Explanation for correct options:

Option (C): Chlorine $\left(\mathrm{Cl}\right)$ is a non-metal and is used for the sterilization of drinking water. It helps in killing all kind of germs present in water and make it portable for drinking.

Explanation for incorrect options:

Option (A): Bromine $\left(\mathrm{Br}\right)$ is the non-metal and is a powerful disinfectant due to its ability to kill the cells of many pathogens.

Option (B): Iodine $\left(\mathrm{I}\right)$is the non-metal which is used as tincture of iodine (a solution of iodine in alcohol) for dressing wounds.

Option (D): Sulphur $\left(\mathrm{S}\right)$ is the non-metal and used in batteries, detergents, fertilizers etc.

Hence, option (C) is the correct answer.