Methyl orange turns red in a solution and phenolphthalein remains colourless. What is the nature of the solution?

Correct answer: Acidic

Indicator colour changes reveal the solution’s acid-base nature. Methyl orange is red in an acidic medium and changes toward yellow as the medium becomes less acidic or basic. Phenolphthalein is colourless in acidic and neutral conditions, becoming pink only in a sufficiently basic solution. Both observations are therefore consistent with an acidic solution. A is correct; a basic solution would usually make phenolphthalein pink, while “metallic” is not an aqueous acid-base classification.