Choose the correct statements.
A. Soluble ions increase turbidity of water.
B. Dissolved oxygen in water changes with temperature of water.
C. Euphotic zone in lake have lowest dissolved oxygen.
D. Benthic zone in lake have low dissolved oxygen and low BOD.
E. Excess algae growth in lakes reduces age of lakes.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B and E only
B is correct: the solubility of oxygen falls as water warms, so dissolved oxygen varies inversely with temperature.
E is correct: excess algal growth (eutrophication) fills a lake with organic matter and sediment and hastens its natural ageing, so the life span of the lake is shortened.
A is wrong because turbidity is caused by suspended, undissolved particles — soluble ions stay in solution and do not scatter light. C is wrong because the sunlit euphotic zone is where photosynthesis occurs and dissolved oxygen is highest. D is wrong because the bottom benthic zone, where organic matter decomposes, has low dissolved oxygen but a high BOD.