JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ev161
Sample P has BOD 3 ppm and dissolved oxygen 7.5 ppm. Sample Q has BOD 20 ppm and dissolved oxygen 2.5 ppm. Use these limits: clean water BOD below 5 ppm, polluted above 17 ppm, DO of about 6 ppm needed for good fish growth, and fish cannot survive below about 4 ppm. Select the correct statements.
AP is classified as clean water
BQ is classified as polluted water
CFish cannot survive in Q
DP has dissolved oxygen below the level needed for good growth of fish
Answer: A, B, C
P has BOD below 5 ppm (clean) and DO of 7.5 ppm, which exceeds 6 ppm, so the last statement is false. Q has BOD above 17 ppm (polluted) and DO of 2.5 ppm, which is below the 4 ppm survival limit for fish.