निम्नलिखित में से कौन सा ऑक्सेलिक अम्ल का एक प्राकृतिक स्रोत है?

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