Step 1: CPWD specification practice.
Marble flooring after polishing is cleaned with a mild acidic solution to remove stains, dirt, and enhance surface shine.
Step 2: Role of oxalic acid.
- Oxalic acid reacts with calcium carbonate present in marble to form calcium oxalate, which gives a smooth and glossy finish.
- It is specifically prescribed by CPWD as the cleaning and finishing agent.
Step 3: Elimination of wrong options.
- (B) Caustic Soda → Strong alkali, damages marble surface. ✗
- (C) Bleaching Powder → Used for disinfection, not polishing. ✗
- (D) White Cement → Used for filling joints, not for cleaning. ✗
Final Answer: \[ \boxed{\text{Oxalic Acid}} \]
Match the buildings in Group I with their corresponding structural systems in Group II. 
