Step 1: Understand the liquation process.
Liquation is a refining method used for metals with low melting points, where the metal is separated by melting it away from impurities.
Step 2: Analyze the given elements.
Tin has a relatively low melting point and can be easily separated from impurities by liquation.
Copper and silicon require other refining methods, while gallium is purified using zone refining.
Step 3: Conclusion.
Thus, tin is obtained in pure form by the liquation process.