9. In a given industrial area there has been a polluting discharge into the river. To evaluate the level of toxicity of the waters, a sample was taken and analyzed in a laboratory. The results of the analysis were: Answer the following questions: A) What information do BOD5 and COD parameters provide us? And the hardness? B) Regarding the solids present in the sample, are they mainly organic or inorganic? Are they suspended or dissolved in water? C) Which parameters should be adjusted so that water can be used as drinking water? D) It is possible that in the vicinity of the river there are, in very low concentrations, gaseous compounds such as CO,CO2,O3 and NO2 in air, what techniques would be used to identify them? (Solution: B) Organic; C) BOD5 and COD )