With reference to furnace oil, consider the following statements:

1. It is a product of oil refineries.

2. Some industries use it to generate power.

3. Its use causes sulphur emissions into environment.

Which of the statements given above are correct?

Why is there a concern about copper smelting plants?

1. They may release lethal quantities of carbon monoxide into environment. 

2. The copper slag can cause the leaching of some heavy metals into the environment.

3. They may release sulphur dioxide as a pollutant.

Select the correct answer using the code given below.