Shaurya accidentally touched a nettle bush during a trekking trip. He felt a stinging sensation and his hand started itching. The instructor immediately crushed the leaf of a dock plant and rubbed it on the affected area, providing relief. What is the nature of the chemical that caused the sting and the nature of the leaf juice, respectively?

Match the substance in Column A with its nature/role in Column B for the reaction: CuO + 2HCl → CuCl2 + H2O Column A: I. CuO II. HCl III. CuCl2 IV. H2O Column B: 1. Salt formed in the reaction 2. Acid reacting with a basic oxide 3. Basic oxide reacting with an acid 4. Neutralisation product

Four test tubes A, B, C, and D are taken with different liquids: A contains glucose solution, B contains turmeric solution, C contains detergent solution, and D contains pure water. Which of the following observations is correct? Observations with: (a) Blue litmus paper (b) Red litmus paper (c) Phenolphthalein indicator