Concept:Acids are substances that change the colour of litmus paper due to their acidic nature.
Explanation:Litmus paper is an acid-base indicator.
Blue litmus paper turns red in acidic solutions.
Red litmus paper turns blue in basic solutions.
Acids do not affect red litmus paper.
Acids do not turn red litmus paper blue.
Therefore, the property of acids is that they turn wet blue litmus paper red.
Option A matches this behaviour exactly.
Answer:A. turn wet blue litmus paper red.