Which one of the following statements is not true ?

1.	Which one of the following statements is not true ?
Answer» Dissolved oxygen (DO) in cold water can reach a concentration up to 10 ppm. Clean water would have a BOD value of 5 ppm. Fluoride DEFICIENCY in drinking water is HARMFUL . Soluble fluoride is often used to bring its concentration UPTO 1 ppm. When the pH of rain water is higher than 6. It is called acid rain. Answer :D

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