A solution that turns blue litmus red is of which nature?

Correct answer: Acidic

Litmus is an acid-base indicator. In an acidic medium, blue litmus changes to red because the indicator responds to the presence of acidic hydrogen ions. Therefore the solution is acidic, so A is correct. A basic solution would turn red litmus blue, while a neutral solution generally produces no litmus colour change. “Salty” describes the possible presence of a salt but does not by itself identify this indicator result.