Answer: one solution is acidic
Step-by-step explanation:
Acid base indicators are usually weak acids or weak bases. They change their color in the solution with change in the pH.
For any indicator say HIn , the dissociation can be shown as:

Litmus is one such indicator which turns red in acidic solutions, blue in alkaline solutions, and purple in neutral solutions.
Thus out of three solutions , the litmus paper strip is turning red in one solution, thus only one solution is acidic. the other two in which litmus is showing blue color are alkaline in nature.