Litmus paper can be used to determine the relative pH of a substance
Answer: Option D
Step-by-step explanation:
The litmus paper is a paper that is used to check of a substance is alkaline or acidic. It shows 2 colors namely the red and the blue. The paper turns blue in color if the substance tested is acidic and it changes red in color if the substance treated is basic. This is built using pigments from lichen that changes color according to the hydrogen ion concentration.