Answer the following questions given below:
A factory produces liquid waste that may be harmful to aquatic life if discharged directly into rivers. Before releasing the waste, it is tested and treated appropriately.
i. The industrial waste may be ________ or ________ in nature.
ii. Which indicator can be used to test the nature of the waste?
iii. Basic industrial waste can be treated with ________.
iv. Why should industrial Basic wastes be treated before being released into rivers?