Match the extraction processes listed in Column I with metals listed in Column II.
`{:(,"Column I",,"Column II"),((A),"Self reduction",(p),"Lead"),((B),"Carbon reduction",(q),"Silver"),((C),"Complex formation and displacement by metal",(r),"Copper"),((D),"Decomposition of iodide",(s),"Boron"):}`

Answer

To solve the problem of matching the extraction processes from Column I with the metals listed in Column II, we can analyze each extraction process and determine which metal corresponds to it.

### Step-by-Step Solution:

1. **Self Reduction (A)**:
- Self reduction is a process where a metal is reduced from its ore without the addition of an external reducing agent.
- Both **Lead (P)** and **Copper (R)** can be extracted using self-reduction.
- **Match**: A → P, R

2. **Carbon Reduction (B)**:
- Carbon reduction involves using carbon as a reducing agent to extract metals from their oxides.
- Both **Lead (P)** and **Copper (R)** can also be extracted through carbon reduction.
- **Match**: B → P, R

3. **Complex Formation and Displacement by Metal (C)**:
- This process typically involves the formation of a complex with a metal ion, followed by the displacement of that metal.
- **Silver (Q)** is commonly extracted through this method, particularly using cyanide complexes.
- **Match**: C → Q

4. **Decomposition of Iodide (D)**:
- The decomposition of iodides can lead to the formation of certain metals.
- **Boron (S)** is extracted through this process, specifically from boron triiodide.
- **Match**: D → S

### Final Matches:
- A → P, R (Self Reduction matches with Lead and Copper)
- B → P, R (Carbon Reduction matches with Lead and Copper)
- C → Q (Complex Formation matches with Silver)
- D → S (Decomposition of Iodide matches with Boron)

### Summary of Matches:
- A (Self Reduction) → P (Lead), R (Copper)
- B (Carbon Reduction) → P (Lead), R (Copper)
- C (Complex Formation and Displacement by Metal) → Q (Silver)
- D (Decomposition of Iodide) → S (Boron)