Camphor, dry ice and iodine undergoes sublimation but silica doesn't so the answer is (c)silica

**Introduction**

Sublimation is the process by which a substance directly transitions from its solid state to its gaseous state without passing through the liquid state. This phenomenon occurs when the vapor pressure of the solid exceeds the atmospheric pressure. Not all substances undergo sublimation, and in this case, we will analyze which of the given options does not undergo sublimation.

**Analysis of the Substances**

(a) Camphor:
- Camphor, also known as C10H16O, is a white crystalline solid.
- It readily undergoes sublimation at room temperature and atmospheric pressure.
- When heated, camphor converts directly to its gaseous form, without melting into a liquid.

(b) Dry Ice:
- Dry ice, also known as solid carbon dioxide (CO2), is composed of carbon dioxide molecules arranged in a crystal lattice structure.
- It sublimes at a temperature of -78.5°C (-109.3°F) at atmospheric pressure.
- Dry ice directly changes from a solid to a gaseous state without going through the liquid phase.

(c) Silica:
- Silica, also known as silicon dioxide (SiO2), is a compound commonly found in nature.
- Silica does not undergo sublimation.
- It has a high melting point of around 1,600°C (2,912°F), so it transitions directly from a solid to a liquid state when heated.

(d) Iodine:
- Iodine is a black crystalline solid that readily undergoes sublimation.
- At room temperature and atmospheric pressure, iodine sublimes into a purple vapor.
- This process is often observed when iodine crystals are exposed to air, and they gradually disappear without leaving any liquid residue.

**Conclusion**

Out of the given options, the substance that does not undergo sublimation is silica (c). Silica has a high melting point and transitions directly from a solid to a liquid state when heated, without passing through the gaseous phase. On the other hand, camphor, dry ice, and iodine all exhibit sublimation, where they directly convert from a solid to a gaseous state without melting into a liquid.