ANS:A - Both A and R are true and R is the correct explanation of A

Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). Explanation:

• Discharging the effluents from oxidation ponds just upstream of lakes or reservoirs is indeed undesirable (Assertion A). This practice can introduce excessive nutrients, organic matter, and potentially harmful substances into the lakes or reservoirs, which can lead to water quality issues and ecosystem degradation.
• The discharged algae from oxidation ponds can settle in the reservoirs and lakes, where they undergo anaerobic decomposition along with other organic matter, impacting water quality (Reason R). Anaerobic decomposition of organic matter can lead to the production of foul-smelling compounds, depletion of dissolved oxygen, and the release of nutrients like phosphorus and nitrogen, which can promote algal blooms and eutrophication.