1. Understand the question

We need to identify the purification method that works on the principle of adsorption.

2. Recall the concept

Adsorption is the phenomenon in which molecules of a substance accumulate on the surface of another substance.

A major application of adsorption in purification/separation is chromatography, where different components get adsorbed to different extents on the stationary phase and hence separate.

3. Check each option

• A: Chromatography
  Chromatography is based on differential adsorption (and partition in some cases) of components between stationary and mobile phases. Hence, this uses the adsorption principle. ✅

• B: Sublimation
  Sublimation is based on direct conversion of a solid into vapor and back to solid. It is not based on adsorption. ❌

• C: Distillation
  Distillation is based on differences in boiling points/volatility. It is not based on adsorption. ❌

• D: Extraction
  Extraction is based on differences in solubility in two immiscible solvents. It is not based on adsorption. ❌

4. Conclusion

Therefore, the purification method based on the principle of adsorption is:

$\boxed{\text{A: Chromatography}}$

5. Comparison with stored correct answer

Stored correct answer: A
Derived answer: A

They match.