`{:(Column-I(Ore),Column-II),((A)"Iron",(p)"Carbon reduction method"),((B)Lead,(q)"Self reduction"),((C)Copper,(r)"Thermite process"),((D)"Chromium",(s)"Hydrometallurgical process"):}`

Answer

To solve the matching question regarding the ores and their extraction methods, we will analyze each ore listed in Column I and determine the appropriate extraction method from Column II.

### Step-by-Step Solution:

1. **Identify the Ore: Iron**
- Iron is primarily extracted from its oxide ore, such as hematite (Fe2O3) or magnetite (Fe3O4).
- The common method for extracting iron is through the **carbon reduction method**. In this process, iron oxide reacts with carbon (usually in the form of coke) at high temperatures to produce molten iron and carbon monoxide.
- **Match:** A (Iron) → P (Carbon reduction method)

2. **Identify the Ore: Lead**
- Lead is extracted from its ore, galena (PbS), through a process that involves roasting to convert it to lead oxide (PbO), followed by reduction with carbon.
- This method is also classified under the **carbon reduction method**.
- **Match:** B (Lead) → P (Carbon reduction method)

3. **Identify the Ore: Copper**
- Copper is extracted from its sulfide ore, chalcopyrite (CuFeS2), through a process called roasting, which converts it to copper(I) oxide (Cu2O) and sulfur dioxide (SO2).
- The reduction of copper(I) oxide to copper metal can occur through a process known as **self-reduction**, where Cu2S acts as a reducing agent.
- **Match:** C (Copper) → Q (Self reduction)

4. **Identify the Ore: Chromium**
- Chromium is typically extracted from chromite ore (FeCr2O4) using the **thermite process**, which involves a reaction between chromium oxide and aluminum powder, producing chromium metal and aluminum oxide.
- **Match:** D (Chromium) → R (Thermite process)

### Final Matches:
- A → P (Iron → Carbon reduction method)
- B → P (Lead → Carbon reduction method)
- C → Q (Copper → Self reduction)
- D → R (Chromium → Thermite process)

### Summary of Matches:
- A (Iron) → P (Carbon reduction method)
- B (Lead) → P (Carbon reduction method)
- C (Copper) → Q (Self reduction)
- D (Chromium) → R (Thermite process)