A knife, which is used to cut a fruit, was immediately dipped into water containing drops of blue litmus solution. The colour of the solution changes to red, what is the nature of the fruit?

The change in the blue litmus solution to red indicates that the substance introduced into the water is acidic in nature.

Explanation (additional Info):

1. The knife was used to cut a fruit, and some of the fruit’s juice likely remained on the knife’s surface.
2. When the knife was dipped into the blue litmus solution, it changed from blue to red, which confirms the presence of an acidic substance.
3. Acids turn blue litmus red, meaning the fruit must have been acidic in nature.
4. Fruits like lemon, orange, mango, apple, and other citrus fruits contain acids like citric acid, ascorbic acid (Vitamin C), or malic acid.