I. Select the Correct Option: 1. The ratio of hydrogen and oxygen in water is: o (a) 2:1 Explanation: The chemical formula of water is H₂O, which means it contains two atoms of hydrogen and one atom of oxygen. 2. An element that kills living germs found in water is: o (b) chlorine Explanation: Chlorine is commonly used to disinfect water and kill harmful germs and bacteria. 3. The most impure water is: o (c) sea water Explanation: Sea water contains a high concentration of dissolved salts and minerals, making it unfit for drinking without treatment. 4. The hardness of water is due to the presence of: o (b) calcium and magnesium salts Explanation: Hard water contains dissolved salts of calcium and magnesium, which cause hardness. 5. Which of the following ...