Step 1: Understanding the cyanide process.
The cyanide process is used for extracting precious metals, especially gold and silver, from their ores. Silver reacts with cyanide to form a soluble complex.
Step 2: Explanation of the options.
- (1) Cu: Copper is not extracted using the cyanide process.
- (2) Na: Sodium is not extracted using the cyanide process.
- (3) Zn: Zinc is not extracted using the cyanide process.
- (4) Ag: Silver is extracted using the cyanide process, forming a soluble complex.
Step 3: Conclusion.
The correct answer is (4) Ag.