AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
(c) Acidic
A solution that turns blue litmus red is acidic in nature. Acids change blue litmus to red.
Source: Introduction, Chapter 2
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The key fact from the textbook introduction: acids change blue litmus to red; bases change red litmus to blue. This is a direct, one-line recall question. Always remember the direction of colour change — blue→red = acid, red→blue = base. "Amphoteric" is not a concept tested at this level in this context.