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.

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Which of the following have species that can establish symbiotic relationship with other organisms?

1. Cnidarians

2. Fungi

3. Protozoa

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