If a solution changes the colour of blue litmus paper to red, what will the pH of this solution be?

Correct option is A

Sol. If a solution changes the color of blue litmus paper to red, it indicates that the solution is acidic. The pH of an acidic solution is less than 7 on the pH scale, with lower values indicating stronger acidity.
 Litmus paper is used to test whether a substance is acidic or basic.
 If the solution changes the colour of litmus from red to blue, it indicates that the solution is basic. For the solution that is basic in nature, the pH is above 7 and lies in the range from 7-14.