(Environmental) please 18,19 and 20

18. What is the major constituents of waste/polluted water discharged from textile, pulp & paper, tanning, distillery, dairy and meat packing industries? a) Radioactive substances. b) Natural organic products c) Inorganic pollutants. d) None of these. 19. If carbon monoxide content in atmospheric air exceeds ppm, death is bound to occur. a) 50 b) 500 c) 1000 d) 3000 (i.e. 0.3%) 20. Determine the 1-day BOD and ultimate 1" stage BOD for a wastewater whose 5-day 20C BOD is 200 ppm. The reaction constant k=0.23 d'. What would have been the 5-day if the test had been conducted at 25C? Note: Write the detail answer. a) 352ppm b) 400ppm c) 224ppm d) 233ppm