A solution turns red litmus blue and gives pink colour with phenolphthalein. What is the nature of the solution?

Correct answer: Basic

Red litmus turning blue is evidence of a basic medium. Phenolphthalein provides a second confirming observation because it becomes pink in a basic solution and remains colourless in acidic or neutral conditions. Since both tests point to the same chemical nature, the solution is basic and option C is correct. A neutral solution would not normally change red litmus or produce the pink phenolphthalein colour, while the last option is contradictory and unsupported.