Acids turn
Ared litmus blue
Bboth litmus papers black
Cblue litmus red
Dphenolphthalein pink
Answer & Solution
Correct answer: C. blue litmus red
1. Litmus is a natural acid-base indicator.
2. **Acids turn blue litmus red**; they leave red litmus unchanged.
3. Bases do the opposite (red → blue).
_Source: Karnataka SSLC (KSEEB) Class 10 Science, Ch2 'Acids, Bases and Salts', §2.1_
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