**Sublimation**
Sublimation is a process by which a solid substance directly converts into a gaseous state without passing through the liquid state. It is a purification technique used to separate a volatile solid component from an impure sample. Naphthalene, which is commonly found in mothballs, is a solid substance that can be purified through sublimation.

**Process of Sublimation:**
The process of sublimation involves the following steps:

1. **Preparation of the Impure Sample:** Start by obtaining an impure sample of naphthalene, which may contain impurities such as dust, dirt, or other non-volatile substances.

2. **Selection of Equipment:** Choose a suitable apparatus for sublimation. This typically includes a sublimation apparatus, which consists of a round-bottomed flask, a condenser, and a receiving flask.

3. **Assembly of the Apparatus:** Set up the sublimation apparatus by attaching the round-bottomed flask to the condenser. Connect the condenser to a water source for cooling.

4. **Heating the Sample:** Place the impure sample of naphthalene in the round-bottomed flask. Apply gentle heat to the flask using a Bunsen burner or a hot plate. The heat should be sufficient to cause sublimation but not high enough to melt the naphthalene.

5. **Collection of Purified Naphthalene:** As the naphthalene sublimes, it vaporizes and travels through the condenser where it cools and condenses back into solid form. The purified naphthalene crystals are collected in the receiving flask.

6. **Separation of Impurities:** The non-volatile impurities that were present in the impure sample remain behind in the round-bottomed flask as residue. These impurities can be discarded, leaving behind the purified naphthalene.

**Advantages of Sublimation:**
- Sublimation is a relatively simple and effective method for purifying volatile solids.
- It does not require the use of solvents or other chemicals, making it a cost-effective and environmentally friendly purification technique.
- Sublimation can be used to separate a wide range of volatile substances, including naphthalene, camphor, and iodine.

Hence, in this case, sublimation is the most suitable process for purifying an impure sample of naphthalene.

Option B could also be correct as naphthalene needs to be cooled after sublimation.
Thus it is same as the process of distillation.
First it is heated then it is cooled.