Which of the following dye is colourless at acidic pH and becomes red at basic pH?
(a) Methyl red
(b) Thymol blue
(c) Phenolphthalein
(d) Phenol red
The question was posed to me in an online interview.
Origin of the question is Isolation and Screening of Industrially Important Microbes topic in division The Isolation, Preservation and Improvement of Industrial Microorganisms of Fermentation Technology