A student dips blue litmus paper into a solution, and it turns red. Which conclusion about the solution is correct?

Correct answer: विलयन अम्लीय है।

Litmus is an acid-base indicator. Blue litmus turns red when it comes into contact with an acidic solution, so the observed colour change shows that the solution has acidic character. A basic solution would turn red litmus blue, and a neutral solution would normally produce no change. The observation cannot prove that the solution is a saturated salt solution. Hence, option A is correct.