Introduction:
In the extraction of copper from its sulphide ore, several steps are involved. The final step is the reduction of cuprous oxide (Cu2O) to obtain pure copper. This reduction reaction can be achieved by using different reducing agents. Let's explore the options given and determine the correct choice.

Options:
A) FeS
B) CO
C) Cu2S
D) SO2

Explanation:

1. FeS:
- Iron sulfide (FeS) is not a suitable reducing agent for the reduction of cuprous oxide.
- FeS is commonly used in the extraction of other metals like zinc, but it does not have the necessary properties to reduce cuprous oxide to copper.
- Therefore, option A is not the correct choice.

2. CO:
- Carbon monoxide (CO) is a strong reducing agent and can be used to reduce cuprous oxide to copper.
- The reaction between CO and cuprous oxide is as follows:
CO + Cu2O → 2Cu + CO2
- This reaction is commonly used in the extraction of copper from its oxide ores.
- Therefore, option B is a potential correct choice.

3. Cu2S:
- Cuprous sulfide (Cu2S) is not a suitable reducing agent for the reduction of cuprous oxide.
- Cu2S is a compound already containing copper in a reduced state, and it cannot further reduce cuprous oxide to copper.
- Therefore, option C is not the correct choice.

4. SO2:
- Sulfur dioxide (SO2) is not a suitable reducing agent for the reduction of cuprous oxide.
- SO2 is commonly released as a byproduct during the extraction of copper, but it cannot directly reduce cuprous oxide to copper.
- Therefore, option D is not the correct choice.

Conclusion:
Considering the given options, the correct choice for the reduction of cuprous oxide to obtain pure copper is option B) CO. Carbon monoxide is a strong reducing agent and can react with cuprous oxide to produce copper.

CuS