CTET 2 Math and Science 1 Jan 2022 Paper

There are three test tubes A, B and C, all having colorless liquid of equal volume and strength. A drop of Phenolphthalein is added to each of them. It is observed that test tubes A and B remain colorless while C becomes pink. When the pink solution of C is added to A and B, it is observed that A remains colorless but B attains pink color. Which of the following is correct inference?