question_answer 1)

  Phosphate containing fertilizers cause water pollution. Addition of such compounds in water bodies causes: (a) enhanced growth of algae                                    (b) decrease in amount of dissolved oxygen in water (c) deposition of calcium phosphate                        (d) increase in fish population

Answer:

  (a, b) Fertilizers containing phosphate; present in the water help in the excessive growth of aquatic plants and algae. Micro-organisms in decomposing these plants consume oxygen. As a result, the amount of dissolved oxygen in the water decreases.