With reference to Eutrophication, which of the following statement(s) is/are correct?1.It decreases dissolved oxygen of water.2.It is a phenomenon of nutrient enrichment of a water body.Select the correct answer from the codes given below.

1. A

   1 only

   (a) 1 only. Dissolved oxygen does fall as algal blooms die and bacteria respire, so 1 is true, but 2 is also the definition of eutrophication.

2. B

   2 only

   (b) 2 only. Nutrient enrichment is the definition, yet the oxygen crash is the linked consequence, so 1 should not be dropped.

3. C

   Both 1 and 2

   (c) Both 1 and 2. Eutrophication is nutrient enrichment of a water body; the resulting bloom and decay consume dissolved oxygen. Both statements are correct, so this is the official key.

4. D

   Neither 1 nor 2

   (d) Neither 1 nor 2. Both the definition and the oxygen effect are standard, so neither is wrong.

Summary. Official key is (c). Eutrophication is nutrient enrichment of a water body and it decreases dissolved oxygen. Both statements are correct.