What is litmus paper's response to sulfuric acid?

• A. Turns red.
• B. Turns blue.
• C. Remains unchanged.
• D. Turns purple.

Answer: (A)

Litmus paper is an indicator that shows whether a solution is acidic or basic by changing color with pH. In acidic solutions, blue litmus turns red, while red litmus stays red. Sulfuric acid is a strong acid, producing a lot of hydrogen ions, so the environment is firmly acidic. This causes blue litmus to turn red, which is why the observed result is red. (Red litmus would already be red in acid, so the key point is the blue paper turning red in an acidic solution.)