Which of the following statements about eutrophication are correct? (i) It can be a naturally occurring process. (ii) It is commonly found in standing rather than running water. (iii) It can lead to oxygen depletion. (iv) It is commonly associated with high levels of phosphates and nitrates.

• A. (iii) and (iv)
• B. (i), (ii) and (iii)
• C. (ii), (iii) and (iv)
• D. All of the above