Which one of the following can be purified by sublimation ? 

Options

A. `F_2`
B. `Cl_2`
C. `Br_2`
D. `I_2`

Answer

To determine which substance can be purified by sublimation, we need to understand the process of sublimation and analyze the given options.

### Step-by-Step Solution:

1. **Define Sublimation**:
- Sublimation is the process where a solid substance transitions directly into a gas without passing through the liquid state.

2. **Identify the States of the Given Substances**:
- We need to consider the physical states of the substances mentioned in the options. The substances in question are iodine, fluorine, chlorine, and bromine.
- **Iodine**: Solid at room temperature.
- **Fluorine**: Gas at room temperature.
- **Chlorine**: Gas at room temperature.
- **Bromine**: Liquid at room temperature.

3. **Determine Which Substance Can Sublime**:
- Since sublimation involves a solid turning directly into gas, we look for a substance that is solid at room temperature.
- **Iodine** is the only substance among the options that is solid at room temperature and can sublime.

4. **Conclusion**:
- Therefore, the substance that can be purified by sublimation is **iodine**.

### Final Answer:
- The correct option is **iodine**.