Answer:
Water pollution may be defined as the contamination of the unwanted substance or pollutant with water that changes the normal characteristics of water. Three main contributors of ground water are as follows:
Chemical farming: The use of pesticides and fertilizers in the fields and its direct run off in river and groundwater causes the water pollution.
Industrial waste: The industrial waste consists of harmful chemicals and heavy metals. The direct discharge of chemical waste in the lakes, ground water and ponds makes the water dirty and causes water pollution.
Effluent from waste water treatment plant: The effluent and the harmful chemical waste release from the waste water treatment plant is the major contributor to the ground water. The effluents mix with the ground water and changes the ground water property.
Easy. Answer is oxygen because it says which one was missing before any life was on earth. And in order to have life on earth you need oxygen!
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More hydrogen ions means more acidic, more hydroxide ions means more basic
O-
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