How many methods of removing the radio active impurities are there?
a) 2 b) 3 c) 3 d) 4
a) 2 b) 3 c) 3 d) 4
a) Oxygen b) Chlorine c) KMnO4 d) Ozone
a) KMnO4 b) MnO4 c) Potassium d) Magnesium
a) Decaying organic matter b) Detergents c) Phenols d) Dissolved oxygen
a) Nitrogen b) Bismuth c) Phenols d) Dissolved oxygen
a) Fertilizer b) Pesticide c) Reagent d) Medicine